The Waldorf oscillators are wavetable-based. There are 64 wavetables to choose from. One wavetable is made up of 64 slots, each slot which can be empty, or contain a wave (a wave being a 128 sample waveform). the oscillator generates sound by scanning thru the wavetable, playing each wave in succession. If there are empty slots in the wavetable, then it calculates an interpolated wave which lies between the previous and next non-empty slots.

For example, if you put a saw wave at wavetable slot 1 and a square wave at slot 64, leaving the rest empty, then tell the oscillator to play position 32 from the wavetable, you'll get a cross between a saw and a square. If you set an LFO to modulate the position in the wavetable, you'll get a sound which sweeps nicely between square and sawtooth.

On the Waldorf oscillator module, you can specify the "startwave" which is simply at what slot (1-64) in the wavetable the oscillator will play. If you patch a modulator to it (e.g. an LFO, or an envelope), then the oscillator will sweep through the wavetable creating very interesting sounds.

The wavetables provided with the Waldorf Oscillator are awesome. The first 8 are the original PPG Wave wavetables. Wavetables 9-30 are from the PPG Wave 2.2, and 31-64 are from the Microwave. Some are nice smooth sweeps (e.g. Resonant, ClipSweep), and some are tables completely filled with different waves so that sweeping thru the table produces really bizarre jumpy sounds (e.g. the Wavetrip tables, Robotic). Some tables have sync sweeps (e.g. SawSync, SinSync, PulSync), and some are pulse-width sweeps (e.g. Micro PWM, PWM Pulse).

You can experiment with the oscillator in the modular by creating a patch with a Waldorf oscillator, a wide open Amp envelope, no filter or anything - just set to the first Wavetable (Resonant 1), and hold a note down while turning the startwave knob. Listen to how it changes as you sweep. Then starting adding envelopes and lfo's to modulate the startwave, and add a filter or two, and you'll have lots of fun.

For more in-depth info, download the Waldorf Micowave II/XT manual (requires Acrobat).