You don't know which ebook format to choose ?
Here are few indications: the epub and pdf formats can both be read on a tablet, an ereader and a computer.
epub has the advantage of adapting to the screens that it's displayed on and of offering reading customizations (font, orientation,etc..) The pdf offers a static and non customizable content.
If you have an Apple device with the IBooks app or one that supports the epub 3, we advise to download this format that will allow you to read/play the music included in this book.
The mobi format is an owned format which presents similar features as epub but can only be read on all Amazon devices ( kindles, and kindle fire).