Could well be in Bb; especially a duet. They made them particularly for people who played with brass and woodwind players; 'transposing instruments' whose music is written with middle C actually sounding like another note. Bb for instance! It would mean the original owner could play a trumpet or clarinet part straight as written and it would harmonise with the rest of the band.
If you're playing solo it doesn't matter; if you're playing with an ensemble you have to go up one on the scale to keep in tune; if you're playing along by ear and they say it's in F you play in G, for example, and if you're trying to play sheet music with a group it gets complicated. Unless you get them to do some trumpet stuff, then you're laughing.
*****Well, I never suspected this when I bought it. Thank you for writing. Do you think that with a reed overhaul that it could be put in C? It needs tuning work anyway, although, right now, I can use it
This would be a whole step up in pitch. This might not be a good idea, especially with some of the higher reeds. But then, I don't have much experience with duets.
****** right, but the buttons are labeled as C but play Bb, for example--which is why this is a surprise to me. Perhaps they can all be moved over to the right place and have some added on at the end? Looks like the Button Box in Massachusetts will have some fun with this one. In the mean while, I will just try and live with this. Thanks for writing!