Quack

Quack is a non-real-time, modular software synthesizer. It allows you to assemble sound generation and modification modules together to generate a wide variety of electronic sound effects and patches.

The output is saved to WAV files.
Quack is modelled on an analog "patch board" synthesizer. It provides a wide variety of audio components - such as oscillators, filters, modulators, envelope generators, noise sources - which can be connected together to produce complex sounds.
Quack can also read in existing WAV files (for example, sounds sampled using Sound Recorder), and incorporate them into sound effects.
Features:
* 19 modules including: Constant, Sine Wave, Square Wave, Sawtooth, Fourier Wave, Noise, WAV Sample, Mixer, Modulator, Merger, Music Modulator, Sequencer, Sweep, ADSR Envelope, Comb Filter, Moving Average Filter, Echo and Fuzz.
* Render to a WAV file of any sampling rate, 8 or 16-bits, stereo or mono.
* Save Patch Maps to proprietary .PM files.