software-base digital instrument.

reason has extensive midi capabilities for creating your own digital music. i've used some of the early betas of doggiebox (a new one was just released today on versiontracker) and it is a very impressive osx native drum machine (and the price is discounted during the beta cycle if you like it enough). i think reason is geared more toward the electronic music than anything else, but i would suggest checking it out further as it may be what you want in terms of a digital instrument bank.

Reason 2 has no audio editing or recording function either, to add to what fattymembrane said...

Reasons sole purpose is to be a combined Midi sequencer and sound generating system, you have analog and digial synths, a sampler (well, 2 actually), a drum machine, REX based loop players (REX files from the reCycle application) as well as mixers and individually patchable FX.

If you want an all in one package that's fairly cheap (note I managed not to say reasonably cheap...) its a winner. Slightly further upmarket, Logic incorporates a range of synth modules and the best software sampler avaliable in the ESX24 sampler, as well as pro sequencing and recording mixing capabilities.

or you could try something like sibelius?

it is a score based program. really good with a full range of midi instruments. can use a keyboard (as in qwerty) or a mouse or a MIDI controller/keyboard (as in CDEFGA).

but it is dependent on how much detail you want to go into to.

and how much debt.