Help! I need advice. I teach music (particularly voice) at the Calcutta School of Music. I use Notation Musician extensively, but I need to (1) alter notes, (2)and also create multiple instrument staves. (3) I will need some assistance for making harmony. I CAN upgrade to Notation Composer for $60. That will not enable me to (4) download MP3 files and turn them into playable midi or karaoke files. (5)I also need the ability to raise or lower the pitch/key of MP3s, to suit the student's range. But if Harmony Assistant can do these things, or many of them, I wd take a deep breath and invest $90.
I don't know the Notation Composer product, but HA will do everything you ask EXCEPT turn MP3s into MIDI or notation. I don't believe there is any product that will do that.
If you just need to raise or lower the pitch of MP3 files, you could do that with Audacity, a free audio editing software.
I use HA to prepare rehearsal aids for a small church choir, and I'm very satisfied with it.
About the mythical "mp3 to score conversion", have a look at http://www.celemony.com/cms/index.php?id=dna It shows a decisive progress in that direction, but it's still far from completion.