If your wondering what gives Acid Techno and Acid House its unique sound then its this monophonic synthesizer: The Roland TB-303
The TB-303 was released by Roland in 1982. It is an analogue oscillator that has 2 waveforms. The TB-303 is used by programming a sequence of notes and timing. It was originally produced for keyboardists, drummers etc but was later picked up by DJs and producers because of its distinctive sound.
The TB-303 was originally used with the 606. Later it was used in line with 808 and 909.
The 2 waveforms the 303 produced was sawthorn wave (simple, single-transister waveshapeing circuit) or square wave .
It uses a simple envelope generator which has a decay control on it. The lowpass filter on it has a -24db octave attenuation and controls cut off frequency & resonance.
The acid sound was created by producers by making the TB303 overdriven to create a harsher liquid sound.