MEK Arpeggiator

Interesting. According to this post on VSE the manual for the MEK includes a section on an Arpeggiator. The PEK and Evolver do not have this.

"Arpeggiator

As a last-minute addition, a simple arpeggiator was included as a hidden function. As
a hidden function, the operation is a little less than obvious, but the assumption is that
it’s nice to have anyway.

Note: The Arpeggiator settings are not saved as part of the Program.

Basic operation is simple: while holding the RESET switch, simply hit the Sequencer 1
switch for an Up direction arpeggio, Sequencer 2 for Down, 3 for Up/Down, and 4 for
Assign, which remembers the order the keys are held. The sequencer switch LED
will blink indicating which mode is currently selected.

Note: You can change modes at any time while playing, or while the keys are
latched.

The Sequencer clock determines the speed, which means it also takes into account
the Clock Divide value. This gives a very wide range of speed, and also enables
swing timing on the arpeggio. And, it can sync to MIDI.
To latch an arpeggio, simple hit the WRITE switch, and the notes will be held when
you remove your fingers from the keyboard. If you then hit another key, it will also be
latched. Hit the WRITE switch again to un-latch.

Note: You can hit the WRITE switch with no keys held, and then just start hitting
the keys you want in the arpeggio, and they will be latched.

Hit the RESET switch to clear the latched notes.

Note: You can only have any specific key played one time in the arpeggio; ie if
you are latching keys, and hit the same note twice, it will only latch the most
recent hit.

To stop the Arpeggiator, simply hit the START/STOP switch."