Set the speed of the song in the range from
400 bpm (beats per minute).
You can use to toggle the metronome.
The volume of the metronome can be adjusted in the Audio tab of the Preferences.
If either Rubber Band support is compiled into your current version of Hydrogen or correctly configured in the General tab of the Preferences, you will also find the button next to the BPM widget. Activating it will enable recalculation of all sample pitches using Rubber Band whenever the tempo of the song will be changed (see Section 12.2 for details).