Access channel strip with latched arpeggio playing

Apologies if this is an obvious one. I have a midi track going out to an external synth, with the corresponding audio coming in through the UMC1820 into an audio track. While the midi track is selected I can play an arp and the audio track plays fine. If I select the audio track the arp, along with keyboard input, stops. If I shift-select the audio and midi track I am able to play the keyboard and go into the audio channel strrip to audition effects, but the arp does not work. Is there a way to to play a latched arp whilst in the audio channel strip or would I need to record a midi sequence?

Okay, found it by hitting the mix button and selecting audio track while the arp is playing.