^
+1
Most studios/engineers/producers I have worked for, at, or with charge on a per album/track basis. In addition if the track is going to be released commercially there is usually some sort of agreement with ASCAP for royalty payments as well.
Rarely do you see a studio that charges on an hourly basis unless they are open to the public for booking. Meaning anyone can look your site up etc. and book with you, most studios though only work within their closed circles because of the risk involved with allowing unknown customers to come through to a studio that houses 1Million+ dollars worth of equipment.
I can’t speak for composers of film and/or tv etc. but my experience comes from working in HipHop and Pop.