Surround Mixing Question

My question is for those MIXING SURROUND MUSIC. How do you guys decide whether to use a surround channel vrs a stereo or mono channel for your 5.1 mix? Is it all based on whatever is sent (some tracks come in mono, others stereo, while others may have been recorded as surround tracks)? If you have a stereo track do you have to upmix it first before you can effectively use it within the project?

What’s your basic routing scheme? It seems logical to me to use stereo and mono tracks, for clearer defined source points, that are then sent to surround busses and then blend them there in a single environment. But I’ve seen many screen shots of mixers using lots of surround channels as well as stereo and mono. But the majority of those sessions were sound design projects, not strictly music. So it just makes sense that there would be a difference.

Could anyone here explain the decision process on which types of channels to use and where to decide when they become surround data in a music mix?

Very difficult question, and one that I do not think has a sensible answer.
In the main, we will use mono/stereo tracks & the v5 panner (or the IOSONO one) which seems to do the job most times. There are other cases where I will need to use a mono file in a 5.1 track though.
The main one is where I need to create an autorotate effect. The best way I have found to do this is with the (sadly defunct) StarPlugs Cyclone Rotator. Drop the mono file into a 5.1 channel, and set up the rotator how you want it to be and then off you go.

Feel free to drop me an email to discuss this further and in more detail