I'm not a Mac user but there have been discussions in the past about the lack of music notation software. I extracted the small snippet from the Melody Assistant Web site. I can't vouch for the program but on the surface its features look quite reasonable and it does offer some niceties such as reading ABC (i think) and producing Tabs. My only area of suspicion concerns how well it produces MIDIs, but it seems to have a lot of satisfied users and it brings out upgrades very often - free, I think.

http://www.myriad-online.com/

It runs on Macintosh (Mac/OS 7.5 to Mac/OS 9, 68020+ or PPC) and Windows (95,98,2000 or NT4). Melody Assistant is shareware, the registration fee is US $15 (or the equivalent in your local currency unit).

I trust that this may be useful to somebody. Regards, John