I agree, it needs to be worked out before hand because of folks who think that mixing a project gives them intellectual rights of the original raw material. In the old days, the mixer/engineer was simply hired guns paid for by the band or their management. They were like roadies and light men, paid to do a job.
Next thing, roadies are going to want the rights for photos taken of a band performing live.....
This is killing me, making the music is the art, the rest of you are like leeches, trying to squeeze every penny out of artists.
Sorry to come on so strong but this has been going on too long. All of a sudden, engineers are the rock stars. Grant you, there are some engineers who deserve the lime light but look through the magazines and their are all kind of guys (most of whom I have never heard of) being paid to be endorsers of this gear or this mic.
This guy and his band should own all of the tracks, raw, stems, final mixes, etc. They made the music and they paid for the service.
Jim