On a music sheet I am reading, the letters "H.V." (without quotation marks) are written occasionally just above specific notes, above the top line of a bar, but lower than where chords are written, and in a smaller font. The music sheet is for trumpet. I have tried googling, as well as looking for it on here, but without finding anything.
Guessing from the acronym and the context, I thought it might mean high volume, but I can't find anything by googling that either.
Thanks for any help