In instruments such as the trombone and slide whistle, moving the slide is the main way of selecting the note while playing.
In instruments such as the trumpet, the slide is moved while playing to help correct the pitch of the note selected by other means.
In instruments such as the french horn, there are many slides used to tune the instrument, sometimes even during practice.
Concerning the tuba, many instruments are built so that the first slide may be manipulated during play. This allows compensation for the flat second-space C, a function of being the fifth partial harmonic of the open bugle.
