When did you see this message? Were you time stretching a sample? Normally you set your tempo when you first start a song. If the tempo doesn't suit you then you can mouse over the tempo at the bottom of the screen and click your mouse to the tempo you wish to use. Also, in song options make sure you have ticked "stretch audio to fit tempo". Please ignore the comment "I have heard a lot of awful music at 120". Beethoven played a fair bit at 120. House music is made at 120 - 130. Driving rock can sit at 120+ (Joe Satriani plays 160+ in some pieces, for example.) Awful music comes in all sorts of tempo and meter.
