Apple always prides itself on catering for creative users. An iApp targeted at people who want to create music ( iPerform ? ) would be an appropriate extension to the iApp family and would mesh very effectively with iMovie, iDVD, iTunes & the iPod.
If it were to offer something like 8 track audio, elementary MIDI and a stripped down version of SoundTrack, it would offer the means for novice musicians, together with those who merely aspire to musical creativity, to create stuff themselves.
Apple have a fantastic track record for taking concepts like that and coming at them in a fresh way, so that the process is great fun and offers impressive results with minimal complexity.
Almost anybody would be able to build a backing track and then record vocals and instrumentals over it using a bog standard Mac with no external hardware ( some Macs will need something like iMic for audio input ).
In the past, Mac users were able to use Digidesign's Pro Tools free, but that is only available for OS 9. Digidesign is reluctant to offer a version for OS X, despite having the full version of Pro Tools working very well on OS X and PT free being available for all modern incarnations of Windows.
Digidesign is owned by Avid, their fortunes have not been improved by Apple's success with Final Cut Pro. I'm not suggesting that Digidesign's new-found disinterest in wholeheartedly supporting the Mac platform is in any way connected to Avid feeling peeved with Apple, but the bottom line is that the lack of Pro Tools Free for OS X leaves a vacuum.
Somebody needs to fill that vacuum and who better than Apple ?
With rumours of a forthcoming Apple audio hardware device nearing completion, it would be a perfect time to launch iPerformer ( or whatever it may be called ) in order to get customers creative juices flowing.
As always, once people start getting pleasing results with the iApp, they will be looking for higher end solutions and will inevitably gravitate towards the new Apple audio hardware device, SoundTrack and Logic. Apple could also generate further income by using the iTMS to sell audio samples to be used as building blocks.
The whole idea could work very well, generating a new market, new customers, new exposure and new income streams for Apple. It would also be a sharp prod in the ribs to a company who had previously been very Mac positive, but are currently less so.