The doit (pronounced "doyt") is a technique used in jazz and contemporary music. When you do a glissando upward after sounding a note, you've done a doit. The half-valve technique helps a lot with this sound on trumpet. In fact, it's essential. Use LOTS of air and blow even harder when you've got the trumpet valves halfway down or the sound won't be heard well.
In this video, learn the techniques necessary to get the most out of this important trumpet skill.
Jonathan Harnum is a musician, author, and teacher with a PhD in music education from Northwestern University. He's the author of several music books, including "Sound the Trumpet: How to Blow Your Own Horn," "Basic Music Theory: How to Read, Write, and Understand Written Music," and "The Practice of Practice."