Soundjack is “a realtime communication system” where musicians can play live together over the internet. My question is, is there a way for two musicians to play over the internet with something like Soundjack and for one of the musicians to record each of the two musicians “communicating “ over Soundjack into separate GarageBand tracks?

If you did get something like that up & running successfully you 'd probably have to use some kind of inter-application routing software like Soundflower [free] or Loopback [$ but more flexible] to direct the audio to the appropriate tracks in GarageBand [configuration would depend on the specific setup]. The Soundjack website had a lot of qualifiers about network connections and 'at least compromised musical interaction' so I don't know how well it would really work on a typical network connection [as opposed to, say, a LAN]..

Thanks for the suggestions! We’ll definitely look into them. As for Soundjack, we aren’t necessarily too invested in this as our final solution so completely open to other types of sound streaming session applications. Soundjack is free so started experimenting there. Actually, kind of surprised there’s not a more obvious existing app that allows two or more people to hear each other over internet while one records separate tracks into their DAW.