There is no "classic" arpeggiator in E! for DX7II. It has "Player" mode, which is crude form of auto-accompaniment/arranger. It plays back pre-programmed sequences (up to 8 tracks), which you can transpose (and sometimes switch between different patterns) using lowest octave on the keyboard. I haven't figured out how to program your own sequences yet, but it probably is covered somewhere in the manual

My main use for E! is memory expansion, so I can have 4 standard DX banks at once
