In any music organization app, there are three layers of sorting.

1. Library / Repository
   1. If you maintain only one Library, here you can see every song you have in a single list
2. Books / Collections / Categories
   1. Subset of songs around a specific topic.
3. Setlists / Playlists
   1. Shorter lists of songs designed for performance on stage. Generally no more than 25 songs (normal concert pace is 10-12 songs per hour).
   2. You can place songs in any order. Libraries and Books always sort alphabetically.
   3. Songs are ‘connected’. This means that when you are finished playing one song a page turn will take you to the next.
4. Other
   1. Tags: Some applications allow you to place tags, or keywords on a song.

So, how does this all translate to real-world use?

I use two apps for music on my tablet. I use one for the choirs I sing in (I participate in three different choirs), and one for the folksinger guitar work I do. The reason for two apps is that choir music is almost always notation; and therefore usually on PDF. Guitar music for me, on the other hand, is almost always lead sheets; and therefore is in text or ChordPro.

Because of the different requirements of each of these uses, I organize choir music and guitar music differently:

Choir	Guitar
Libraries: 1	Libraries: 1
Books / Collections: One book per choir, one book for guitar songbooks that I have scanned to PDF	Books / Collections: Mostly used to organize music I have written vs music written by others. There is a separate book for Twotonic songs; as well as separate books for humorous songs and songs that everyone can sing to.
Setlists: One setlist per gig	Setlists: One setlist per gig
Tags: Not used	Tags: Lightly used, usually to identify different songs that have a similar topic (i.e. songs about Trains)