The tempo window allows you to control the tempo at any point your song. It can be opened by selecting Windows -> Tempo from the song window. The tempo can range from a value of 1 to a value of 400.
The tempo window is a variation on the track window, so the controls and operation are similar, although some controls aren't applicable: Since there are no other tracks, the saturation control will not affect anything. Since tempo changes do not have velocity, the velocity button will not do anything. Since a song is always required to have an initial tempo change, you can not move or erase the first tempo. Finally, the wand tool has no effect on tempo events.