I picked this up to work on a new instrument to me (Bb trombone). It's not possible to set it up to read the notes you're actually playing from the music staff on a Bb instrument like a trumpet or trombone. You can alter its idea of an A (440hz) but only by a little more than a semi-tone flat or sharp - not the whole tone required to correctly display the note being played on a Bb instrument. I find that a little bit disingenuous - it says right on the box "Designed to accommodate the Trumpet and Trombone". Also, mine came with a clamp that will only open about 3/8" - so it'll clamp fine to a bell, but not to, say, a guitar's headstock. The directions however suggest clamping it to the main tube (lead pipe) of a trumpet. That's just not possible using the clamp in the one I received. So, is it useful - sure. But you have to transpose constantly, and it doesn't give you an indication of which octave you're playing in either (a little bit of an issue on the 'bone for me). It's annoying for me, probably disastrous for a beginner to keep transposing, while trying to play and see if they're in tune. This tuner does stay 'on' for up to 30 minutes after you stop playing. My guitar tuners don't - so that's a plus vs a standard guitar tuner if you're paying attention to each note you play, and not just the initial coarse tuning of the instrument's main tuning slide.