Using the Playback Track you can program your song alongside an existing audio file, for example a guitar track.
When a Playback Track is loaded, it will be played back every time audio transport in Hydrogen is rolling and Song Mode is activated.
To add a playback track to your song, you need to enable the playback track view. This can be done by either pressing left of the scroll bar at the bottom of the Song Editor or via the View element of the Main Menu.
Left to the wave display, the controls of the Playback Track are displayed.
: loads an audio file.
As an alternative, you can load an audio file by dragging it into Hydrogen and dropping over the Playback Track.
: mutes the Playback Track.
: adjusts the volume. You can think of this fader as the mixer strip of the Playback Track. The resulting audio will be passed into the Master section of the Mixer like any other strip too.