I think the best bet is to make an html file, that way you can format the lyrics in an acceptable format, although due to font size limitations, some lines will have to be split into two or even three (you don't need three lines on purely space / size considerations, but you may want to do this to at least keep the song verses / stanzas in a logical order.) Also, if even some of the verses have very lengthy lines it would best not to centre them but to keep them left justified, this way releases more width to fit more in.

If you have image files of the basic scores / dots, then do consider uploading them in an oblong shaped file but rotated right by 90 degrees; in Word terms, Landscape orientation. It will mean folks having to turn their screen on one side, but apparently millions do this anyway for charts, table, maps etc, so it's nothing new to the Kindle / EReader world.