Here's how to adjust the Volume level for one of the Songs in the TD-15.
1. Press the SONG button and then choose a desired Song.
2. Press the MENU button.
3. Press the function 1 button (Volume).
4. Turn the dial to adjust the volume.
5. Press EXIT when you're finished. The new setting is saved in the song automatically.
Repeat the steps for any other songs if desired.