It should be possible to add an arp as bluearp or other midi note processing effect(jamstix 4 or other drummer software with midi output) in same way as can do with the buildin arp or repeater in the multiinstruments. I report this to S1 support as a bug, because normaly think this should work too, but they told i should do a feature request in Forum. so if you like this feature too please vote.