Jon-M awhile back asked for tunes that exercise arpeggios. I’m not very good at inventing a great variety of arpeggios and progressions of them for my own personal practice, so I found a freeware program that generates more than I’ll ever master. I think it will help me make up my own tunes in the future.
http://reglos.de/musinum/
This isn’t just a keyboard arpeggiator.