When the music stops and then restarts but at a new tempo, your work as a conductor is relatively straightforward since you have time to prepare. You have to be very sure of your new tempo AND anticipate it by giving a faster - or slower - preparatory beat at the new speed.

Conduct bars 1-15 of Bartók’s “Van Egy Gyűrűm, Karika” (“I have a ring, Karika”), showing the opening Allegro tempo (144 bpm). During bar 6, prepare for the next Pesante tempo of 132 bpm with a slower upbeat on the second beat of the bar. Stop on the downbeat of bar 15.