Oct-21
Stations for Wave study and visualization
Last week's “exploratorium” session provided some shots of string resposnse to an excitation (-1- -2- -3- -4- -5-) which were surprisingly good. I didn't think the strobe was going to work out. Numerical simulation of an excited string can produce similar motion in time steps (piano string velocity, Chaigne 1994). Notice here where the blur of the pink rope is moving in time and makes it possible to interpret the traveling wave direction. We also lucked out and caught the tablecloth in action quite nicely. These show propagation of waves in 2D (-1- -2- -3-) ala a membrane like a drum head.
The outdoor clapping experiment used Snd to measure the speed of sound between a mic and a nearby whiteboard surface. Sandwiching the mic between two boards creates a ping-pong, repeated echo train (aka, IIR) at 5ms and was recorded by one of the groups in this waveform.
Clips from Compositions Featuring Real-time Interaction
Mesias Maiguascha, The Nagual (1993)
Jonathan Impett, Mirror Rite (article 1998)
Jean-Claude Risset, Eight Sketches for Disklavier (1989) description
David Jaffe and Andy Schloss, Wildlife (Stanford Centennial performance 1991) this excerpt is from the mp3 recording online
V
Edible Trance
(4:17 min )
HW3: Interaction Engines
We're starting simple. The interaction in HW3 will be limited to signals from mics and input from computer keyboard and mouse.
Engine etude: Explore FreqTweak to manipulate live sound, storing and loading different “scenes” with its preset facility. Perform an improvisation combining this with live players or demo this as the platform for a sound installation piece. Record a short performance ahead of class. Post to homework factory.
Programming a Pd engine: Create a new Pd patch for algorithmic interaction. Demo in class. Make a direct audio recording of the patch in action. Post to homework factory. Algorithmic means
Example Pd algorithm – pitch vs. timbre streaming illusion
Isorythm is a technique in music where complex phasing is played out between streams in different musical dimensions. In the medieval version, it was melody of one length vs. rhythm of another length (in terms of number of notes). The shape vs. color (3 against 4) diagram above shows the same idea at work. In our Pd example, we use FM synthesis to generate 3 timbres and 4 pitches. Tempo can be changed to increase or decrease the proximity effect which splits timbres into different streams, or “voices.”
The timbres of the FM tones alternate between:
sinusoidal
inharmonic (multiple partials, ambiguous pitch)
harmonic (fused partials, tuned harmonically, one pitch)
Example FreqTweak Engine – Lots 'o delays, frequency dependent
test tone from
...insert screen shot here...
Title: Duet for one pianist : eight sketches
Creation date: 1989
Duration: 14 to 15 minutes
Premiere: May 1989, The Cube, M.I.T.
Instrumentation: Interactive acoustic piano (Disklavier) and pianist
This is probably the first piano "duet" for a single pianist: in addition to the pianist's part, a second part is played on the same piano - an acoustic piano, with keys, strings and hammers - by a computer which follows the pianist's performance. This requires a special piano - here a Yamaha Disklavier - equipped with MIDI input and output. On this piano, each key can be played from the keyboard, but it can also be activated by electrical signals: these signals trigger motors which actually depress or release the keys. Each key also sends out information as to when and how loud it is played. The information to and from the piano is in the MIDI format, used for synthesizers. A Macintosh computer receives this information and sends back the appropriate signals to trigger the piano playing: the programming determines in what way the computer part depends upon what the pianist plays.
In these eight sketches, I have tried to explore and demonstrate different kinds of live interaction between the pianist and the computer.
Double. The pianist plays alone, then on the repeat the computer adds ornaments. These are prerecorded: they are called when the pianist plays certain notes; their tempo can be influenced by the tempo of the pianist.
Mirrors. Each key played by the pianist is echoed by a key stroke, symmetrical with respect to a certain pitch - a process used in Webern's second Variation opus 27, quoted at the beginning (and also at the end with time reversal). The symmetry center and the response delays are changed during the piece to vary the effects.
Extensions. To the arpeggios played by the pianist, the computer adds additional notes transposed in pitch.
Fractals. To each note played, the computer adds five notes spaced approximately - but not exactly - one octave apart. Thus the pitch patterns played by the pianist are distorted in strange ways: an octave jump is heard as a semitone descent.
Stretch. Pitches are added, as in Extensions, but the intervals are not merely transposed: they are stretched by a factor ranging between 1.3 and 2.7. This extends the harmony as well as the melodies played by the pianist.
Resonances. At the beginning and the end, the computer plays long sustained chords. In the middle section, the pianist plays mute chords: the strings are set in resonance by the sequences played by the computer.
Up Down. Quasi-octave arpeggios are triggered by the pianist, whose few notes can thus generate many notes. The tempo of the arpeggios is set first by the tempo of certain patterns played by the pianist; later by the pitch he plays; then by the loudness.
Metronomes. This begins by a short canon: the computer echoes the pianist on transposed pitches and at different tempos. It later plays simultaneously different sequences at different tempos. Then it repeats the same pitches, but again at different metronomic tempos, either preset or set by the pianist.
This "duet for one pianist" was realized in 1989 as I was was composer in residence in the Music and Cognition Group, Media Laboratory; M.I.T., thanks to a grant of the Massachusetts Council of the Arts. It was implemented with the real-time program MAX written by Miller Puckette at M.I.T. and at IRCAM. I acknowledge the highly dedicated and competent help of Scott Van Duyne.