What Steve Gardham said.

> 1. decided,
That comes from the lead musician who should be sufficiently experienced to pretty much 'know' what speed they need to set off at. They will be working closely with the caller on any adjustments required as the dance goes on.

> 2. generated
The lead musician plays the intro, and everyone else starts at the speed set by the lead musician. If someone in the band disagrees with the lead musician and wants to play at a different tempo, then they should debate that offstage, and are perfectly at liberty to go and be the lead musician of their own band that plays things faster / slower.

> 3 maintained.
The lead musician is primarily responsible for that too. If other musicians can't play the chosen tunes at the speed required for the dances, they shouldn't be playing those tunes for the dancing. Depending on the instrumental line up, the availability of decent on-stage monitoring, etc., the drums and bass etc may have a special responsibility in this respect as they may be the elements of the band that are most immediately communicating the tempo to the other musicians and the dancers; but ultimately the responsibility lies with everyone, and anyone who doesn't like it is again perfectly at liberty to go and start their own band that plays things faster / slower.

All the above is deliberately black-and-white and rarely if often has to expressed in such terms - but if you are playing for dancing you are playing for dancing, which means that the core purpose of your presence as a musician is to provide music suitable for and fitted to the dance.