A few excerpts from the Poly Evolver manual:
"The sequencer can be triggered in a variety of ways, including via its own internal clock, by the keyboard, or with an external audio signal."
"If the sequencer is Off, hit the Tap Tempo four times, and on the fifth hit the sequencer will start with the speed set according to the timing of the taps. If you keep hitting it, or otherwise hit it while playing, the sequence speed will change to match the tap speed."
"Press the START/STOP switch to start the sequence."