What does the balancer do on a trombone?

The balancer on a trombone helps to improve the balance and intonation of the instrument. It consists of a weighted slide that moves through a housing, which is attached to the trombone's slide. By adjusting the position of the balancer, the player can adjust the weight distribution of the instrument, which can help to make it more comfortable to play. Additionally, the balancer can be used to adjust the intonation of the trombone by changing the position of the slide.