JSyn - modular synthesis API for Java.
JMSL - Java Music Specification Language
PortAudio - cross platform audio I/O API for 'C'

Audio Examples made using JSyn - a Java Synthesizer API

Modulated Sawtooth

How it works:

The sound you hear is being generated by an SawtoothOscillator unit. The frequency of the sawtooth is being modulated by a TriangleOscillator  running at a low frequency.
ModRate controls the frequency of the Triangle LFO ("Low Frequency Oscillator").
ModDepth controls how much the Sawtooth frequency is modulated by the LFO.
CenterFreq controls the frequency of the sawtooth before modulation is applied.
HalfLife controls the decay time of an exponential lag generator.  It determines how long it takes the output to decay half way to its target value. This Lag function can be forced to a high value using the "Ping" button.  The lag function then decays to its input level, in this case 0.0, with the specified half life.

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