My own version of Song of Storms (sequence is 1-2-3 for intro, repeat 4-5-6 for main melody; sadly not all the harmonies are possible with the current note-set, and there aren't enough pages to get the tag exactly right): http://notepad.cc/share/jheYg8TA8I
(continued--sorry, I guess I'm feeling a bit verbose) I'd also like to see a chromatic scale, melodic minor, etc.--or even some more exotic ones like octatonic. If you could use different scales on different pages (or even between instruments, a la Prokofiev or Ginastera or other moderns), that would be awesome. (And as has been said in quite a few other comments, it would also be great to have a mute button, a way to disable the echo, and a custom percussion track.)
It would be really nice to be able to choose different scales/modes to use for the tone row (for non music theory geeks, this just means picking different sets of notes to use). The similar program here (http://lab.andre-michelle.com/tonematrix), which has been mentioned in a couple other comments, uses a pentatonic scale, which basically makes dissonance impossible even if you write tone-clusters (again, for non-theory people, this means that any random collection of notes written with this set of notes will probably sound good no matter what). One nice thing about this is that it makes it easier for people without musical training to write cool pieces; another advantage is that it allows for a broader pitch range (the gadget I linked to covers just over three octaves, while the one here only covers a little over two).
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