GB2460278A

GB2460278A - Directing the movements of a visually impaired performer around a stage

Info

Publication number: GB2460278A
Application number: GB0809446A
Authority: GB
Inventors: Virginia De Ledesma
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-05-23
Filing date: 2008-05-23
Publication date: 2009-11-25
Anticipated expiration: 2028-05-23
Also published as: GB0809446D0; GB2460278B

Abstract

An apparatus is provided for assisting the movement of a visually impaired performer 4 on a stage 2 during a performance of a musical and/or dramatic work. During a rehearsal of the work, the position of the performer 4 is detected whilst following a desired path. Data indicative of the desired position of the performer 4is stored via a computer 14 as a function of time with respect to the performance of the work. During a live performance, the computer 14 processes data indicative of time with respect to the live performance of the work, desired position data, and actual position data, to calculate data representative of how the performer 4 should move. Signals are provided indicating movements that the performer 4 should make to follow the desired path. The signals may be provided via a signalling vest which comprises four infrasound transducers located around the performer's body. The position of the performer may be determined by multilateration by means of a beacon 20 and base units 18.

Description

Stage navigation aid This invention relates to methods and apparatus for directing the movements of a visually-impaired performer around a stage.

There have been many initiatives to encourage and facilitate disabled involvement in the performing arts. Technology can play a key role in ensuring the success of such initiatives. The present invention is concerned with means by which a blind or visually-impaired performer such as a singer or actor can be guided around a stage during the performance of an opera or other musical or dramatic work, without the direct intervention of another human being, so that the blind or visually-impaired performer will be able to participate safely and confidently in an opera, play or the like.

From a first aspect, the invention provides a method for assisting the movement of a visually impaired performer on a stage during a performance of a musical and I or dramatic work, comprising the steps of: (i) during a preliminary performance of the musical and / or dramatic work, * ::: :* 20 providing a first sensing system for detecting the position of the performer on the * ,* stage using a sensor carried by the performer; providing assistance for the performer to follow a desired path; using the first sensing system to detect the position of the * performer whilst following the desired path; and storing desired position data * * : :* indicative of the desired position of the performer on the stage along the desired path, as a function of time with respect to the performance of the musical and I or dramatic work; and (ii) during a live performance of the musical and I or dramatic work, providing a second sensing system for detecting the position of the performer on the stage using a sensor carried by the performer; providing the performer with signalling means which provides signals that can be sensed by the performer so as to guide movements of the performer; using the second sensing system to detect the position of the performer at points in time during the live performance and to provide actual position data indicative of the position of the performer at said points in time; using data processing means to process (a) data indicative of time with respect to the live performance of the musical and / or dramatic work; (b) the stored desired position data; and (c) the actual position data, so as to calculate, for a given point in time during the live performance, required movement data representative of how the performer should move subsequent to that point in time in order to follow the desired path; and using the required movement data to control the signalling means in order to provide the performer with signals indicating movements that the performer should make in order to follow the desired path in the live performance of the musical and / or dramatic work.

The method of the present invention allows a visually-impaired performer to first record a route around a stage during a dress rehearsal, cued or synchronised to a musical soundtrack or to spoken lines, and then subsequently, during a performance, be guided along the same route in a manner that is invisible to the audience and that is minimally distracting to both the visually-impaired performer and to other * 20 performers. Because the route is linked to a soundtrack, the guidance can take account of variations, such as changes in tempo or differing-length pauses between * performers' entries, in the timing of the actual performance compared with the dress rehearsal. *

In preferred embodiments, during a performance apparatus implementing the *::::: method of the invention can run in a largely automated fashion; i.e. without *.: requiring the involvement of a human assistant, beyond perhaps initialising the apparatus at the start of the performance or after an interval. Similarly, during a preliminary performance (or dress rehearsal), the path of the performer may be captured without significant intervention by a human assistant or operator. The method of the present invention therefore allows a visually-impaired performer to rehearse and perform alongside sighted performers in as independent a manner as possible; i.e. without imposing a large burden on other performers or theatre staff in order to compensate for the performer's disability. Apparatus for putting the invention into effect may be portable; in particular, all the apparatus needed to carry out the method of the invention is preferably together able to be carried by hand by the performer when not in use.

Preferably, providing assistance for the performer during the preliminary performance of the musical and I or dramatic work can be achieved by providing the performer with an obstacle sensor which detects the presence of obstacles and provides the performer with information concerning the positions of obstacles. The obstacle sensor can preferably also detect the front edge of the stage area, beyond which there may be a drop to a lower level. It may also be able to detect the back of the stage area, which may comprise a boundary wall, and may also detect other borders to the stage area, such as the side edges adjacent the wings, The obstacle sensor may be a simple cane, but preferably uses sound waves, radio frequency waves, visible light detection, or infra-red light detection. In particularly preferred embodiments, the obstacle sensor uses ultrasound waves; it may, for example, be an UltraCane from Sound Foresight Limited. * **

During the preliminary performance the desired position data may be stored as a function of absolute time from a given point in the musical and / or dramatic work, and during the live performance of the musical and I or dramatic work the data :. indicative of time with respect to the live performance indicates absolute time from * 25 the given point in the musical and I or dramatic work. The given point may be the : start of a musical section in a musical work, or may be the start of an act or scene in a dramatic work.

Manual intervention may be used to synchronise timing during the live performance of the musical and I or dramatic work with timing during the preliminary performance of the musical and I or dramatic work (a) at pre-selected points in the work, and / or (b) in response to noted substantial timing differences between the live performance and the preliminary performance, and / or (c) in response to noted interruptions in the live performance.

Alternatively, a sound tracking system is provided; the desired position data are stored as a function of points in the musical and I or dramatic work that are identified by the sound tracking system during the preliminary performance; and the data indicative of time with respect to the live performance of the musical and / or dramatic work indicates points in the live performance that are identified by the sound tracking system as corresponding to points identified by the sound tracking system in the preliminary performance of the musical and / or dramatic work. The desired position data may be stored as a function of relative time from a preceding point in the musical and / or dramatic work that is identified by the sound tracking system.

The sound tracking system may comprise a microphone and sound processing means for detecting passages of music or speech. When the musical and/or dramatic work is an opera, in preferred embodiments only the instrumental sound track is used by the sound tracking system; i.e. the sound tracking system does not attempt to determine the words being sung by the performer. These embodiments are advantageous in that there is thus no need for a microphone to be worn by, or situated close to, the performer.

L: :* The passages to be detected are preferably input to the sound processing means as a musical score or a written script. Alternatively or additionally, when the work is a musical work, the sound tracking system may comprise a musical beat detector * : ::: arranged; beat detection may be achieved by analysis of recorded sound, or a conductor may hold an electronic baton arranged to indicate downbeats and / or other beats to a processing means.

When a sound tracking system is provided, it may nonetheless be desirable that manual intervention be used to provide data to the sound tracking system for synchronisation purposes during the live performance of the musical and / or dramatic work (a) at pre-selected points in the work, and / or (b) in response to noted substantial timing differences between the live performance and the preliminary performance, and / or (c) in response to noted interruptions in the live performance.

The signalling means is preferably wearable; and may for example be concealable in use under the performer's clothing. In this way the signalling means will not be apparent to the audience. The signalling means may emit audible signals; however, preferably it operates inaudibly; e.g. by means of nerve stimulation. It may therefore, for example, comprise heating means; vibration means; means for electrically stimulating the performer's nerve endings; an inflatable bladder; or other touch stimulation means. In some embodiments it comprises a subsonic acoustic emitter arranged to emit subsonic impulses towards the performer's body.

The signalling means may signal direction by comprising multiple signal-generating elements which may be arranged on various parts of the performer's body; for example on the performer's stomach, back, left flank and right flank. In this example, only a single impulse would be required to indicate a direction of movement that the performer should make in order to follow the desired path in the live performance of the musical and / or dramatic work. Alternatively or additionally, coded instructions may be sent to the performer using multiple :: : impulses; in this case the signalling means need only comprise a single signal-generating element (although it may comprise more). * *. * I S * S

:. The first sensing system and the second sensing system may be the same or different. Either sensing system may use any suitable technique, well known to the person skilled in the art, to detect the position of the performer at points in time *.: during the live performance. One or more sensors, such as RFID tags, may be fixed to the performer. The sensors may be active (having their own power sources) or passive. The sensing system may comprise a plurality of base stations in wireless communication with a sensor located on the performer. The sensing system may send radio-frequency, ultrasonic or infrared signals between a base station and a sensor. These signals may travel in only one direction; e.g. the sensor being a beacon that emits regular pulses, or may travel in two directions; e.g. a base station polls one or more sensors which respond. The sensing system may then use information relating to time-of-flight to determine the location of the performer on the stage; for example using known methods such as multilateration or ellipsoid-intersection. In this instance, the location of the base stations with respect to the stage area is known to the sensing system.

Alternatively, the sensing system may comprise a reference-point unit, a pedometer located on the performer, and means for determining the direction in which the performer is facing, the reference-point unit and pedometer being in wireless communication with a server and the reference-point unit comprising indications for the placement of one of the performer's feet in a predetermined reference position with respect to the stage area. The reference-point unit is preferably located in a fixed position off stage; for example on the floor of one of the wings. It is preferably arranged to indicate to the server when one of the performer's feet are located in the predetermined reference position. Preferably the reference-point unit comprises two recesses for receiving respective ones of the performer's feet in a predetermined orientation. It will be appreciated that such a system can determine an estimate of the performer's position on the stage from information relating to the number of steps taken by the performer since leaving the reference-point unit and :.::: the direction in which each of said steps has been taken. Between on-stage appearances, the performer may return to the reference-point unit, allowing the L: :* sensing system to compute subsequent position information from a known reference point.

* : ::: Advantageously, during the live performance of the musical and / or dramatic work, * e obstacles on the stage are provided with sensors, the sensing system detects the positions of the obstacles and provides obstacle position data to the data processing means, and in calculating movement data representative of how the performer should move, the data processing means uses the obstacle position data to avoid collisions between the performer and the obstacles. An obstacle may be static, such as a table; may be a moveable prop (theatrical property), such as a chair; or may be another performer.

Preferably the data processing means uses information relating to the layout of the stage in calculating movement data representative of how the performer should move to avoid the performer reaching or moving beyond an edge of the stage.

In some preferred embodiments, the signalling means is arranged to provide the performer with a signal indicating imminent collision with an obstacle and / or a signal indicating imminent arrival at an edge of the stage; preferably this signal is different from (e.g. more forceful or urgent than) the signals indicating movements that the performer should make.

Preferably the musical and / or dramatic work is a musical theatre work (commonly known as a musical) or an opera; and the performer is a singer. The invention is particularly applicable to opera because an opera typically has a musical timeline for whenever a performer is on stage; i.e. an opera has few or no passages of spoken dialogue or complete silence. This allows a sound tracking system to determine data indicative of time with respect to the live performance of the musical and / or * 20 dramatic work solely by analysing the music. Therefore, in preferred embodiments in which the musical and / or dramatic work is an opera, the sound tracking system *.* * * does not track speech. * ** * S S

Alternatively the dramatic or musical work may be a ballet and the performer may beadancer. * S. * S S * *S

* : . . In some embodiments, manual intervention is used to provide a conductor in respect of the live performance of a musical work with an indication of a noted substantial difference in timing between the live performance of the musical work and the preliminary performance of the musical work. In this way the conductor may be alerted to excessive variations in tempo that may cause difficulties for the performers, in particular for the visually impaired performer.

The indication may be visible such as the illuminating of a light visible to the conductor. There may be two lights -one to indicate that the live performance is, while the light is illuminated, being conducted at a faster tempo than was used at the same point in the preliminary performance, and the second to indicate that it is slower. Alternatively, a light capable of separately emitting two different colours may be used similarly.

In embodiments in which a sound tracking system is provided, as described above, preferably the dramatic or musical work is an opera, the performer is a singer, and the sound tracking system is a music tracking system which tracks musical points in the opera. Desirably musical point data from the music tracking system are used together with absolute time data to provide a conductor in respect of the live performance of the opera with an indication of a substantial difference in timing between the live performance of the opera and the preliminary performance of the opera. This indication may use light as described above.

Preferably the points in time during the live performance at which the position of the performer is detected are separated by intervals, each interval being, for example, about at least 1 second long but preferably no longer than, for example, about 30 ::: seconds to 1 minute long. Alternatively, the points in time may have negligible * ** separation between adjacent points in time; i.e. they are almost continuous. * S. * . S

The required movement data representative of how the performer should move subsequent to a point in time in order to follow the desired path is preferably *: *::* calculated taking into account the actual position data from a plurality of earlier * * * points of the points in time. It is preferably calculated taking into account the stored desired position data from a plurality of points of the points in time. The calculation may involve determining a predicted trajectory or bearing of the performer, determined from the actual position data. If the performer is determined not to be on the desired path, the required movement data is preferably calculated to bring the performer back onto the desired path; advantageously, it is calculated to bring the performer directly back onto the desired path; however, the required movement data may be subject to predetermined constraints, e.g. avoiding instantaneous changes in direction greater than a certain angle or radius of curvature.

From a second aspect, the invention provides apparatus for assisting the movement of a visually impaired performer on a stage during a performance of a musical and / or dramatic work arranged to carry out the steps of the method of the first aspect of the invention.

From a third aspect, the invention provides a sensing system for detecting the position of a visually impaired performer on a stage during a performance of a musical and / or dramatic work comprising a sensor carried by the performer.

Preferably the sensing system comprises means to detect the position of the performer whilst following a desired path during a preliminary performance of a musical and / or dramatic work. Advantageously the sensing system further comprises means to record desired position data indicative of the desired position of the performer on the stage along the desired path, as a function of time with respect to the performance of the musical and / or dramatic work.

S.'::' From a fourth aspect, the invention provides wearable signalling means arranged to * S. * provide signals to a performer during a live performance of a musical and / or dramatic work, wherein the signals can be sensed by the performer so as to guide * movements of the performer.

* From a fifth aspect, the invention provides data processing means arranged to * process (a) data indicative of time with respect to a live performance of a musical and / or dramatic work; (b) stored desired position data indicative of the desired position of a performer on a stage along a desired path, as a function of time with respect to a preliminary performance of the aforesaid musical and / or dramatic work; and (c) actual position data indicative of the position of the performer at points in time during the said live performance, so as to calculate, for a given point -10-* in time during the live performance, required movement data representative of how the performer should move subsequent to that point in time in order to follow the desired path.

From a sixth aspect, the invention provides a software product arranged to be run on a data processing means so as to cause it to carry out the process described above.

Preferably the software product is stored on a portable medium such as a USJ3 storage device or a CD-ROM. In this way it may easily be carried by the performer.

The performer may thus be able to transport the software product to a venue and load it onto a data processing means, such as a laptop computer, already in situ at a venue in order to carry out the method of the invention.

For all of the above aspects, the preferred features of any one aspect are to be understood as being equally applicable, mutatis mutandis, to any of the other aspects.

A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: *: :: Figure 1 is a perspective diagram of a theatre arranged to carry out the method of the present invention; * *. * S S

Figure 2 is a flow chart of the rehearsal part of a process embodying the method of the invention; and * .. * S S * S.

Figure 3 is a flow chart of the live performance part of the process of Figure 2.

Figure 1 shows a theatre stage 2 on which an opera is being rehearsed. A visually impaired opera singer 4 and a sighted opera singer 6 are performing. The stage also contains a table 8 which is a prop for the scene being performed. In front of and below the stage is an orchestra pit 10 in which an orchestra is being lead by a conductor 12.

A computer 14 and operator 16 are situated off stage. The computer 14 is in wireless communication with base units 18, which are part of an RF-based time-of-flight tracking system. There are preferably at least three base units 18 located around the stage 2. The visually impaired performer 4 wears an RF beacon 20 arranged to transmit RF pulses at regular intervals, having an internal clock that is synchronised with a clock onboard the computer 14. The sighted performer 6 also wears a similar beacon 22, preferably operating on a different channel or frequency to the first beacon 20 so as not to cause interference. The table 8 and other props may also carry beacons.

The conductor holds a baton 24 arranged to communicate wirelessly occurrences of downbeat strokes to the computer 14. A microphone 26 is connector to the computer 14 and is angled so as to pick up music from the orchestra pit 10.

The computer 14 is arranged to recognise passages of music received via the microphone 26 and to use signals from the baton 24 to assist in this recognition process. The complete musical score of the opera is stored by the computer 14 in a format appropriate for such recognition. *.IS * 0 *0.*

* :* Turning now to Figure 2, the various steps performed by the computer 14 during the * rehearsal are set out in the flowchart, which will now be described with reference to 0** the apparatus of Figure 1. * ** * * I * *S

* * * When a rehearsal is underway, the computer 14 monitors the position through the score by analysing information relating to the musical sound waves and musical beats captured by the microphone 26 and the conductor's baton 24. From this monitoring, a periodic determination of time within the performance is made 50.

-12 -Once a time stamp has been determined (which may be in terms of bar number and beat within the bar since the start of a musical section) 50, the position of the visually-impaired performer 4 is determined 52 by means of a multilateration calculation performed by the computer 14. This calculation is based on the times taken for the most-recently emitted RF signal from the beacon 20 to reach each of the base units 18. These times can be determined directly from the times at which each base unit 18 detects the signal, since the computer 14 knows the time at which the signal was emitted (because the beacon 20 and computer 14 have synchronised clocks). Alternatively, if no synchronised clocks are available, time difference of flightcanbeused.

The position of the performer on the stage is then saved 54 as a time-stamped waypoint in the computer's memory. A sequence of such waypoints effectively plots the performer's route around the stage throughout the rehearsal. The visually-impaired performer 4 may, during the rehearsal, use an aid such as an ultrasound cane (not shown) or a human assistant (not shown) to determine and navigate a preferred route avoiding obstacles such as the table 8.

The position of other sensor-equipped objects, such another performer 6 or a prop such as a table 8, may also be saved in the same step 54 as saving the time-stamped * PS ** waypoint in respect of the visually-impaired performer 4. **.* * S S...

If the rehearsal is not indicated by the computer operate 16 as having finished 56, * the above steps 50, 52, 54 are repeated, possibly after a predetermined time delay.

* ::* Figure 3 shows the steps performed during a live performance of the previously- *: * rehearsed work. During the performance, the performer 4 dispenses with any obvious mobility aids such as an ultrasound cane arid instead dons a signalling vest (not shown) hidden under his or her costume.

During the live performance, the computer 14 monitors the position through the score by analysing information relating to the musical sound waves and musical -13 -beats captured by the microphone 26 and the conductor's baton 24. From this monitoring, a periodic determination of time within the performance is made 60.

After a given time determination, the waypoint having the next-closest timestamp is retrieved 62 from the computer's memory.

The position of the performer is then determined 64 using the previously-described method. Similarly, the position of other tracked objects, such as the other performer 6 and props such as the table 8, may also be determined at this step 64.

From the determination of the performer's present position, and optionally also from the history of several prior positions, the speed and course of the performer is estimated 66. The performer's position, speed and heading are checked against the next waypoint retrieved previously 62, and optionally also against previous and subsequent waypoints to this one, to determine 68 whether the performer is following the desired path (i.e. the path followed during the rehearsal).

If the performer 4 is on the correct path; i.e. is expected to reach the next waypoint, and the performance has not yet finished 72, the above steps 60, 62, 64, 66, 68 are repeated.

s* * If the performer 4 is not expected to reach the next waypoint, an appropriate direction indication is sent 70 to the performer 4 via the signalling vest, which comprises four infrasound transducers located around the performer's body, which, when activated, can inform the performer 4 of the need to move more to the left, more to the right, more forwards or more backwards. II 4 S *4

If the computer 14 determines that a collision with another performer 6 or an object 8 is imminent, or that the edge of the stage is being approached, is imminent, the transducers can emit an alarm signal to the performer 4 and / or a more forceful direction signal. Alternatively or additionally, the computer 14 may be arranged to -14-calculate a new desired route, deviating from the first desired route in order to avoid a collision.

It will be readily understood that the flowchart steps in Figures 2 and 3 need not necessarily be performed by the computer 14 in precisely the order shown, and that some degree of parallel processing may be appropriate. The human operator 16 is able to override the computer's automatic behaviour in case of a malfunction or to allow for some unexpected eventuality in the theatre. * SI * S * * *5 * 5* * S S *S S. * a*. *

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S * S* * S * S * S. * * S S

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Claims

-15 -Claims 1. A method for assisting the movement of a visually impaired performer on a stage during a performance of a musical and / or dramatic work, comprising the steps of: (i) during a preliminary performance of the musical and / or dramatic work, providing a first sensing system for detecting the position of the performer on the stage using a sensor carried by the performer; providing assistance for the performer to follow a desired path; using the first sensing system to detect the position of the performer whilst following the desired path; and storing desired position data indicative of the desired position of the performer on the stage along the desired path, as a function of time with respect to the performance of the musical and / or dramatic work; and (ii) during a live performance of the musical and / or dramatic work, providing a second sensing system for detecting the position of the performer on the stage using a sensor carried by the performer; providing the performer with signalling means which provides signals that can be sensed by the performer so as to guide movements of the performer; using the second sensing system to detect the position of the performer at points in time during the live performance and to provide actual *::: position data indicative of the position of the performer at said points in time; using * , data processing means to process (a) data indicative of time with respect to the live performance of the musical and / or dramatic work; (b) the stored desired position *.* data; and (c) the actual position data, so as to calculate, for a given point in time *: *::* 25 during the live performance, required movement data representative of how the * ** : performer should move subsequent to that point in time in order to follow the desired path; and using the required movement data to control the signalling means in order to provide the performer with signals indicating movements that the performer should make in order to follow the desired path in the live performance of the musical and I or dramatic work.

-16 -
2. A method as claimed in claim 1, wherein providing assistance for the performer during the preliminary performance of the musical and / or dramatic work comprises providing the performer with an obstacle sensor which detects the presence of obstacles and provides the performer with information concerning the positions of obstacles.
3. A method as claimed in claim 2, wherein the obstacle sensor uses sound waves, radio frequency waves, visible light detection, or infra-red light detection.
4. A method as claimed in claim 1, 2 or 3, wherein during the preliminary performance the desired position data are stored as a function of absolute time from a given point in the musical and I or dramatic work, and during the live performance of the musical and / or dramatic work the data indicative of time with respect to the live performance indicates absolute time from the given point in the musical and / or dramatic work.
5. A method as claimed in claim 4, wherein manual intervention is used to synchronise timing during the live performance of the musical and / or dramatic work with timing during the preliminary performance of the musical and I or dramatic work (a) at pre-selected points in the work, and / or (b) in response to noted * substantial timing differences between the live performance and the preliminary ". performance, and / or (c) in response to noted interruptions in the live performance. S...
6. A method as claimed in claim 1, 2 or 3, wherein a sound tracking system is provided; the desired position data are stored as a function of points in the musical *: *::* and / or dramatic work during the preliminary performance which are identified by * the sound tracking system; and the data indicative of time with respect to the live performance of the musical and / or dramatic work indicates points in the live performance which are identified by the sound tracking system as corresponding to points identified by the sound tracking system in the preliminary performance of the musical and / or dramatic work.

-17 -
7. A method as claimed in claim 6, wherein manual intervention is used to provide data to the sound tracking system for synchronisation purposes during the live performance of the musical and / or dramatic work (a) at pre-selected points in the work, and / or (b) in response to noted substantial timing differences between the live performance and the preliminary performance, and / or (c) in response to noted interruptions in the live performance.
8. A method as claimed in any preceding claim, wherein during the live performance of the musical and / or dramatic work obstacles on the stage are provided with sensors, the second sensing system detects the positions of the obstacles and provides obstacle position data to the data processing means, and in calculating movement data representative of how the performer should move, the data processing means uses the obstacle position data to avoid collisions between the performer and the obstacles.
9. A method as claimed in any preceding claim, wherein the dramatic or musical work is an opera and the performer is a singer.
10. A method as claimed in claim 9, wherein manual intervention is used to provide a conductor in respect of the live performance of the opera with an * indication of a noted substantial difference in timing between the live performance of the opera and the preliminary performance of the opera.:.: *
11. A method as claimed in claim 6 or 7, wherein the dramatic or musical work * 25 is an opera, the performer is a singer, and the sound tracking system is a music * : :* tracking system which tracks musical points in the opera. ** * * * S

* 1
12. A method as claimed in claim 11, wherein musical point data from the music tracking system are used together with absolute time data to provide a conductor in respect of the live performance of the opera with an indication of a substantial difference in timing between the live performance of the opera and the preliminary performance of the opera.

A

-18 -
13. A method as claimed in any preceding claim in which the first sensing system and the second sensing system are the same.
14. Apparatus for assisting the movement of a visually impaired performer on a stage during a performance of a musical and I or dramatic work arranged to carry out the steps of the method of any of the preceding claims.
15. A sensing system for detecting the position of a visually impaired performer on a stage during a performance of a musical and I or dramatic work comprising a sensor carried by the performer.
16. A sensing system as claimed in claim 15 comprising means to detect the position of the performer whilst following a desired path during a preliminary performance of a musical and / or dramatic work.
17. A sensing system as claimed in claim 16 further comprising means to record desired position data indicative of the desired position of the performer on the stage along the desired path, as a function of time with respect to the performance of the musical and / or dramatic work. * ** * * S * **

*
18. Wearable signalling means arranged to provide signals to a performer during S...a live performance of a musical and / or dramatic work, wherein the signals can be L: sensed by the performer so as to guide movements of the performer. S..

*: ::*
19. Data processing means arranged to process (a) data indicative of time w'ith * * respect to a live performance of a musical and I or dramatic work; (b) stored desired position data indicative of the desired position of a performer on a stage along a desired path, as a function of time with respect to a preliminary performance of the aforesaid musical and I or dramatic work; and (c) actual position data indicative of the position of the performer at points in time during the said live performance, so as to calculate, for a given point in time during the live performance, required -19 -movement data representative of how the performer should move subsequent to that point in time in order to follow the desired path.
20. A software product arranged to be run on a data processing means so as to cause the data processing means to carry out the process claimed in claim 19. * ** * S S * ** **** * S * *5 * * S *5I SS * * S. * S * * *S * *S S S S *S