I stumbled upon this program that lets you compose music like mario paint. It also allows you to convert your creation to MML format for your games I think. This japan user has created a couple games and an 8 by 8 font editor to change the look of text.
Composer QR code http://d.hatena.ne.jp/eidaht/20120630/1341016869
How to use composer (you need google translator to read it) http://d.hatena.ne.jp/eidaht/20120701/1341122770
Youtube videos of sample songs made with composer http://d.hatena.ne.jp/eidaht/20120701/1341123345
Font editor QR code http://d.hatena.ne.jp/eidaht/20120325/1332696941
Missile Defense QR code http://d.hatena.ne.jp/eidaht/20120321/1332350715
Minor Miner QR code http://d.hatena.ne.jp/eidaht/20120408/1333909708
Retro Racing QR code http://d.hatena.ne.jp/eidaht/20120314/1331737108
This user also has other QR codes but, I don't know what their intended uses are.
Would anyone mind walking through how to play the music made using the composer in applications? Songs saved using it are GRPs by default, and even though I'm sure the data is actually MML, I don't know the correct command to copy to a BGM. Any help is much appreciated!