An improved arbitrary waveform generator has a waveform memory for storing digitized waveforms, a waveform playout for playing out desired ones of the digitized waveforms as analog waveforms and a sequencer for controlling the waveform playout, the sequencer providing indications of the desired waveform for playout and a desired starting sample position for the desired waveform. The sequencer includes a tracking mechanism for the desired waveform so that the desired waveform is phase coherent when playout is interrupted and restarted later according to programming of the sequencer.