They don't have basic support for the chromatic scale (except maybe the speak?). I have used the po-14 sub which has C major scale plus an "effect" that lets you add other notes using the sequencer (tricky to do), and po-33 KO! which has a tunable natural minor scale plus sharp 7th degree. If you are an experienced musician at all and enjoy playing in a chromatic scale, I don't think I can recommend the POs as a stand-alone instrument. The Speak apparently has a scale setting and modulation, so it might be more interesting but I haven't used it.