Movement Study

Movement Study employs the DIEM Digital Dance system. Software written by the composer using the MAX programming environment interprets the incoming data, allowing the dancer's movements to control and influence the music. In the first and last sections, a slow polyphonic texture is established in which the computer determines tonal material while the dancer controls the volume and frequency spectrum of eight drones. In the middle sections, the computer produces the tonal and rhythmic material, while the activity levels of the individual voices are controlled by the move-
ment activity of the dancer.
The first sketch of the piece was composed in collaboration with the choreographer Warren Spears and presented at a workshop organized by DIEM and Nyt Dansk Danseteater in Copenhagen in 1996. A new version was developed with choreographer and dancer Helen Saunders, who premiered the work in a concert version at the Aarhus NUMUS festival in April, 1997. This work was further developed by dancer Pernille Fynne and performed at ICMC97 in Thessaloniki, Greece in September, 1997.

Movement Study II: composition description
In the first section changes in angles of the ankles, knees, elbows and wrists are mapped directly to amplitude (volume) and filter parameters (brightness) of eight different long drone notes, one for each of the eight limbs. When an elbow is for example bent to its minimum angle or 'closed', no tone is heard. As it is opened (angle increased) the tone becomes louder and brighter and then softer and darker as it is closed again. If a limb is closed completely, a new note event is triggered and a new pitch and timbre chosen by the computer program the next time the limb is opened.
The harmonic structure is determined by a set of compositional rules. There are seven subsections consisting of seven different harmonic structures or chords. In any one subsection each voice has a limited number of possible pitches (for example 3) that might be chosen in that subsection (only one note per voice can be played at any time) according to a set of pre-defined probabilities for each of these pitches occurring. The choices made by the composition software are tightly controlled random choices. On the one hand no one can predict exactly which pitches will be played at any given moment within a particular subsection, on the other hand it is certain that the pitches chosen will lie within the harmonic structure for that subsection.

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Movement Study II software, main screen. ©Wayne Siegel 1997
The seven harm onic structures cannot be influenced by the dancer. The dancer can however influence the speed at which the piece progresses through the seven subsections before finally reaching the second section. Movement from one subsection to the next is based on the number of new note events triggered by the dancer. The more often the dancer's limbs are placed in the closed position, the faster the program moves to the next subsection. If limbs are never completely closed, the computer will remain within the current subsection allowing the dancer to manipulate volume and brightness only of pitches contained in this subsection. It is, for example, possible for the voice associated with the right wrist to remain in subsection 1, while the left knee is in subsection 2 and the right ankle in subsection 5. This would mean that the pitches chosen by these various voices would not lie within a single harmonic structure. This ÒincongruityÓ might be corrected by software in the course of the performance. If the limb of a voice that has fallen behind is finally closed, the software will skip to the highest section currently being used by any other voice. Or, in the example above, the next time the right wrist is closed it will skip ahead to section 5, the section that the right ankle has already reached.
The first section of Movement Study II gives the dancer direct control of two very perceptible paramaters: volume and brightness for each of the eight voices. But the dancer does not make choices related to melody, harmony or rhythm. This gives the dancer a certain amount of freedom of movement as well as expressive control of the music without requiring excessive concentration on instrumental performance.

Section 2
In the second section, activity of knees, elbows and wrists are mapped to activity of eight voices in a contrapuntal texture of pluck-like sounds. Activity is defined as the change of angle over a particular period of time. If the angle of an elbow changes say from 45¡ to 49¡ within an 80 ms. period, then the activity for that period is defined as the difference between the the two angles: the greater the difference between the present angle and the previous angle, the greater the activity. The computer generates random rhythms in which the number of notes played by each of the eight voices is directly related to the activity of the associated limb.The choice of harmonic material is related to the technique used in the first section, where subsections with different harmonic structures set the harmonic framework for each individual voice and coordinate interplay between voices. This section serves as a transition between the first and third sections.

Section 3
In the third section activity of knees, elbows and wrists are mapped to activity in a pulse-based six-voice contrapuntal texture.Six polyphonic percussive voices are controlled by the knees, elbows and wrists (angles of ankles are not used for this section). A fixed, regular pulse is set by the computer, and the six voices are always rhythmically synchronized. A 10/8 meter is implied in the software with pitch probabilities for all voices defined for each of the 10 beats as well as pitch probabilities for sixteenth notes which can occur between the eight note beats. Pitch choices are made on the fly by the computer program according to the composition algorithm; there are no predefined sequences.
The dancer controls only the activity of each of the six voices, not the musical material to be played. The greater the activity of a particular limb at a given moment, the greater the probability of a note being played by the associated voice at that moment. The more the dancer moves, the more notes will be filled into the implied 16th note matrix. If the dancer stops moving, probabilities drop to zero and no notes are played: the music stops immediately. The tempo is fixed, but can be influenced slightly by the dancer: increased overall activity (average activity of all six limbs) increases the tempo slightly.

Section 4
This section is similar in construction to the first section, although the tonal material used in the two sections is different. The other main difference is that in some of the subsections this section, the angles of each joint controls pitch bend as well as volume and brightness for the associated drone. This allows the intonation to change for each voice seperately (+/- a quarter tone).

Transitions
Since the four sections of the piece use very different types of mapping of the dancer's movements, the transition between sections was an interesting problem to address. Two different approaches were chosen for the three transitions. The transition between the first slow section and the second random rhythmic section consists of an overlap. The eight seperate voices change sections independently, so that the left elbow might start section two while the right elbow is still in section one. An override fade function is built into the software, so that all of the drone voices of section one finally fade out slowly after section two is underway. The transition from section two to section three is similarly an overlap, while the transition from section three to section four is abrupt. When the dancer moves into a certain position on the stage, section three stops with a loud gong-like sound and section four fades in.

Choreography
An essential idea in Movement Study is that the dancer is able to influence musical processes and not simply trigger sequences and events. Since the compositional program and digital dance system were developed first, the task of the choreographer was to experiement with the hardware and software to get aquainted with the ÒinstrumentÓ and then begin to develop a choreographic idea that could integrate an artistically viable choreography with the movements necessary to control the music. The dancer must also be given a certain amount of freedom if she is to be able to react to the music and directly influence the music. Although the system has been used by choreographer/dancer teams, it seems that the best results can be achieved when the dancer and choreographer are one and the same person. This allows the choreographer to try out the instrument in a Òhands onÓ situation to gain a better understanding of how various movements influence the music. Through the process of direct experimentation a fixed choreographic form and structure could be developed. The choreographer was thus created as a choreographic study within the framework of movement dictated by the hardware and software. The dancer is placed in an entirely new situation, with the responisbility of interpreting both musical and choreographic ideas and integrating them into a single work.