TubeNet

58mark wrote:This a fairly new miraphone 186 that played fine last week.

That's a big clue right there. First thing I'd want to eliminate would be a leaky water key.

"... checked the horn for alignment"? Exactly how did you do that? Unless you actually LOOKED at the alignment through the tuning slides, it may still not be aligned correctly. Alignment marks are sometimes not entirely reliable.

The leaky water key is always a good idea, but I'd expect it to show up on more than a couple of notes.

jsmn4vu wrote:

58mark wrote:This a fairly new miraphone 186 that played fine last week.

That's a big clue right there. First thing I'd want to eliminate would be a leaky water key.

Spin the horn a few times and see what comes out. One time at Dillon's, I tried a brand new Miraphone 188. It was an okay horn, but didn't play great. Then I decided to spin it, and out comes 1 styrofoam packing peanut. After that, problem fixed, and it was an extremely fine horn!

guess: Ab and C use first valve on a BBb tuba. something's lodged in the first valve tubing or there's a leak in the first valve circuit somewhere.

Have you done a leak test on it?