The Structure of the Trombone
How to play the scale

Trombones work by using the slide to change the length of the tubing, which controls the pitch of the sound. The slide has seven positions, counted in order from the 1st position (toward you) to the 7th position (fully extended). However, there are no position markers on the tubing. Trombone players learn the positions by feel. Although guitars have positions (frets) on their necks, trombones are more like violins, which do not. Trombones are therefore not so unique in terms of position markers (or lack thereof).

Just because there are seven slide positions doesn't mean that trombones can only play seven sounds. A trombone can produce several sounds from a single position.
Let's listen to what kinds of sounds can be produced from the 1st position.

The sounds produced at each position, from 1st to 7th, are shown below, expressed as notes:

A trombone player varies the sound produced at a single position by changing how he or she blows into the instrument. Trombones do not have finger holes, so a trombone player changes the sound with his or her mouth rather than his or her fingers. The more a trombone player tightens his or her lips, the higher the pitch produced.
Notes are played on a trombone through a combination of the slide position and the way the player blows into the instrument.