I got this explanation from a web page:

An arpeggiator is a tool/feature available in some hardware synthesizers and also in software form, which allows the user to play alternating notes or chords automatically based on input, most often from a midi controller. An electronically created arpeggio. Arpeggiation is also available in some sequencer software and virtual instruments.

I had a Kawai keyboard that had this on it and I believe my MZ-2000 had it also.

-Linda