I have been using EasyBeat to compose music on my Mac. It is MIDI based although you do not need a MIDI device to use it. I love it because there is mulitple way to write your music. You can write it in TABs, Keyboard View, or stright Score writing. I love it and found that it is well worth the money. I like being able to write music and then print it out in standard form. EasyBeat IMHO is way better then GarageBand's, ( which I thought was a letdown ).
Writting Music with your Mac
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