I’ve been really digging into this lately.
According the spec for the MIDI Start Real-Time message, after receiving a Start command a device is only supposed to actually Start when it receives the next MIDI Clock pulse. The device should wait in a pending state until a Clock pulse is received.
I’ve confirmed that both EHX and Pigtronix loopers, and a DAW sequencer, implement this standard. If I really want to send a command to start those loopers regardless of whether MIDI Clock is present, they have CC commands for that (which, of course, target those units via a Channel).
Aeros takes a non-standard approach the Start Real-time message and actually starts (playing or recording) immediately upon receiving the command. This makes things a bit unorthodox if you are using an external MIDI clock and real-time messages to manage your performance, especially when you are aiming to sync a couple audio loopers or sequencers together and all but 1 conform to the standard (Keep in mind that Real-time messages are not bound to a Channel, so every device in the MIDI signal chain will respond to them and should do so in a standard way.).
Looking at the Aeros, I think a possible solution is to add a 3rd value to the MIDI IN:START setting. I’m not sure what you might call it, but basically the setting would be for those of us who need it to behave according to the standard, which to restate: A Real-time Start places the device into a pending state waiting for the next MIDI Clock pulse to be received.
Thanks. I can help research and discuss other kinds of options.