There are two main types of trombones: valve and slide trombones. On valve trombones you can press buttons to change the notes with the help of valves, which means, every note has a fix button combination. On valve trombones the player has to learn the seven positions of the slide with its distances. There are no stops or signs for these positions, the player has to be aware of how far he/she must pull the slide for the desired note.