If I'm not mistaken, the format of the music is basically already a PDF file. The music is offered by "FreeHand" which has offered a dedicated sheet-music reader for several years.
I have often relished using the DX for reading music. However, the timeout is an issue. To make it really useful, Kindle will have to come up with a way to disable the timeout because it depending on what you are playing/practicing, it would be a pain to have the thing keep switching over to the screen saver.
MusicPad Pro Plus -- $899.
• Size: 13.3" x 9.9" x 1.8" (just over 4 lbs.)
• Easy-to-read, low glare, touch screen
• 12.1" TFT LCD back-lit, color display eliminates need for external music stand lighting
• Resolution: 1024 x 768