The background sheet is awefull. It's all wrinkled and sagging. And the top of the instrument is cutoff! And the subject looks like she's standing on one leg for some reason. LOL.
in reality your exposure of the suject ispretty nice though a catch-light on the hair would be a good addition. However, in 99% of all portrait work, the background should just about always (if not always) be at least blurred out in the DOF at a minimum. The wrinkles and the pin-up point just above the finger area is a strong detraction as well. Now to the subject, its a general bad feeling to cut off any part of the subject that is a strong focus point, and in this situation the flare of the horn should be in frame. However, a great portrait is either a FACE, a PERSONALITY or both, but most importantly it should generate a feeling for the person, not the photo.
Nice try but it is too obviously posed and the model appears ill at ease with the instrument. The face is also the last thing my eye comes to rest on since the frame is dominated by the rest of her body and the shiny trumpet.
The backdrop is a bit messy also in the bottom left. A drape of this kind is fine but put it slightly out of focus by using a narrow depth of field in order to lose the wrinkes and focus more attention on the model.
I play too but not often enough! Nice idea but perhaps the subject should be further away from the background to drop it out of focus and Imaybe I would crop to the waist and not crop the trumpet, giving a landscape portrait of a trumpet player - great!