Roland AT900 Music Atelier Owner's Manual page 266

Enjoying Music and Video
6.
Touch <
You can touch Play Transpose <
When you touch Melody <Mute> in the screen, the melody will be muted.
You can mute the melody, and play the melody yourself.
When you touch Melody <Guide> in the screen, the volume of the melody will be
lowered. You can leave the melody playing at a lowered volume and play along until
you've learned the melody. Since you will still be able to hear the melody, you can use
it as a guide during practice.
7.
Touch <
264
> to start playing back the song.
>< > to change the key of the song.
> to stop playing back the song.