To get back to on topic...

The thing that confuses me the most is, why audio backing at all? Because of the uneditable nature of them, surely professionally produced SMF's are the FAR more useful option?

I would have thought that recording accurate audio backing tracks would be MUCH more expensive to produce than MIDI tracks. Even if you assume that Yamaha (or whoever) hire great musicians to PLAY the drum and MIDI guitar Parts (and all the keyboards, of course), you don't need a fully equipped studio to do it in. This has GOT to drastically reduce the cost of production. Not to mention the cost of a real horn section, backing singers etc..

Now, after all that, you end up with a product that can easily be edited by the customer, he can easily mute out parts he wants to play himself (or herself!), he can change the sounds if he wants, restructure, basically anything he wants.

So.... WHY?