The same song can carry different playback settings in each playlist it belongs to: its key, style, tempo, and repeats.

 

So one playlist can hold a bossa version in F and another the original ballad, each remembered on its own. Set them from the player while the song is open in that playlist.

 

Transposing a song inside a playlist works the same way, and the key is remembered for that playlist alone. This is a soft change that leaves the chart untouched; to change the key the chords are written in, see Transpose a song.

 

For more, see Organize your songs into playlists on the iReal Pro website.