amplitude modulation

Video: YouTube: Drancing accelerometer music with Wiimotes: 3D variable frequency oscillators + amplitude variation + triggered "air drum" samples

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Demonstrates combined oscillator frequency variation, amplitude variation, and triggered Drum sample ("Drumming by Dancing") modes along with Drancel RGB monitor visuals projected onto the "Drancer" performer.

For this demonstration two hand-held WiiTM Remotes on a MacBook Pro were used. (The original Drancing accelerometer suit (since 1997) used 5 triaxial accelerometers in a "body star" pattern").

Video: YouTube: Drancing accelerometer music with Wiimotes: 3D amplitude (volume) variation + triggered "air drum" samples

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Demonstrates combined amplitude (volume) variation, and triggered drum samples ("Drumming by Dancing", "air drums") modes along with Drancel RGB monitor visuals projected onto the "Drancer" performer. Includes stereo echo with constant timescale and some feedback.

For this demonstration two hand-held WiiTM Remotes on a MacBook Pro were used. (The original Drancing accelerometer suit (since 1997) used 5 triaxial accelerometers in a "body star" pattern").

Video: YouTube: Drancing accelerometer music with Wiimotes: 3D variable frequency oscillators + triggered "air drum" samples

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Scenes

Demonstrates variable frequency oscillators + triggered drum samples ("Drumming by Dancing", "air drums") modes along with Drancel RGB monitor visuals projected onto the "Drancer" performer.

For this demonstration two hand-held WiiTM Remotes on a MacBook Pro were used.

A composite JSyn software component that performs real-time audio synthesis with AM or VFO

A composite JSyn software component that performs real-time audio synthesis with AM or VFO

So now the acceleration signals are acquired and conditioned let's use them to modulate some synthesised sound with JSyn audio:

To really understand this audio synthesis one should study the JSyn API and tutorial. A brief explanation follows:

  • A slight smoothing lag is required in the modulating acceleration signal otherwise one can get sharp "clicks" caused by a jump in the modulation, since the data acquisition loop is fast enough for bumps to be heard as audio spikes !
  • The modulating signal is distributed (fan-out) and conditioned separately (scaled and offset) for VFO and AM. Of course one can play many other games like trimming and such, too, however scale and offset is sufficient for proof-of-concept.
  • One can choose between "fixed" amplitudes and frequencies or modulated amplitudes and frequences, to achieve: pure AM, AM + VFO, or pure VFO. The idea of this prototype is to demonstrate these pure modes, however of course many other syntheses are possible. The "fixed" amplitudes and frequencies can actually be varied by the user as system parameters using UI controls, so they are named here "varAmplitude" and "varFrequency". They are effectively "fixed" on the timescale of the synthesis engine compared with the slow GUI cycle.
  • The modulating or "fixed" frequency and amplitude are then fed to an oscillator (in this case a simple sine oscillator).
  • A further gain is applied, which achieves the mix into the final bus.
  • The modulated oscillation is panned to stereo bus writers for combination with other stereo syntheses in the final output mix.

With NACC=5 triaxial accelerometers (15 channels) the effect is to synthesis body movements, postures, and gestures into a rich composite sound that promotes strong aural biofeedback !

Groups of three user parameters can be master-slaved to a single UI control to impose "triaxial accelerometer" structure for the user experience. Or one can group all X, Y, or Z channels and act on those, or one can group all channels for global UI control.

Video: Drancing suit 2002: variable frequency + variable amplitude mode

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The (X,Y,Z) channels of five 3D accelerometers vary the amplitudes and the frequencies of 5 x 3 = 15 pure sinusoidal oscillators.

One can hear "beat" frequencies generated by similar frequencies corresponding to different accelerometer channels, such as when the arms are raised to similar levels, which effect can be exploited for musical nuance and for movement therapy to measure symmetry of posture.

Video: Drancing suit 2002: amplitude (volume) variation of the notes of a triad chord

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The (X,Y,Z) channels of five 3D accelerometers vary the amplitudes of notes of fixed (C,E,G) chords at different octaves. When the amplitude varies by small amounts about a larger mean value (such as when waving the arms about a common raised level) the mode can be said to represent Amplitude Modulation (AM).

This is a subtle mode, and care must be taken to sufficiently distinguish the notes of each chord triad. Amplitude variation can also be well combined with other modes such as variation of the frequency of oscillators.

Video: Drancing suit 2002: triaxial accelerometer sound axes: variable frequency and variable amplitude modes

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Demonstration of the axes of a triaxial accelerometer using sound synthesis. The relationship to gravity is explored using vector acceleration with 3D Variable Frequency Oscillator (VFO) mode, then amplitude variation "triaxial chord" mode.

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