This is going to sound a little weird.
I recall a long time ago seeing some old movies (it might have even been the Little Rascals), in which a person on stage playing a trumpet (or trombone, I’m not sure which), was unable to continue his performance when he saw someone in the audience sucking on lemon slices.
Is this just on-screen craziness, or could a lemon-sucking audience member really spoil one’s trumpet recital?
Supposedly the sight of a lemon being eaten would cause a sudden spike in saliva production, because if that lemon were in your mouth the very tart taste of the citric acid would need dilution and pH buffering which is provided by saliva. And a sudden increase in saliva in the trumpet player’s mouth would mix with the airstream and spoil the clean tone of the instrument. Brass players have to drain their horns periodically of all the saliva they blow into them under normal conditions as it is.
I have played in bands but never seen this phenomenon in real life. Just imagining the taste of a fresh lemon, though, see if you don’t notice any increase in saliva production.
Not just brass players - many curved wind instruments have spit valves for draining the curved areas that can’t use gravity for drainage.
Straight wind instruments, while not usually having a spit valve still have to have their inside walls dried down before putting them away.
As far as the OP, my old HS band director regaled us with this one time, only a) he never mentioned it as being limited to brass instruments - this “could happen” to any wind instruments and b) he said it was because the pucker face people made would make the musician think about his embouchure (the shape his lips need to take to take around/on the instrument’s mouthpiece to form a proper sound on the instrument) too much and start flubbing it.
Of course, when pressed, it turned into a good ol’ FOAF type recounting, so I don’t buy it. And thinking about it, I know for me that when I was performing I was concentrating too much on the performance to pay any attention to what was going on outside of the orchestra even on the rare occasions I could see beyond the stage lighting
I don’t see it working. You have to have your lips puckered to play a trumpet anyway. The best I can describe it is you blow like you’re giving somebody the raspberry, but keep the tongue in your mouth. The Little Rascals used over the top humor with pranks that didn’t work the way the show portrayed it.
I could see how watching someone eat a lemon could make a person’s mouth muscles tense up (whether into a pucker or to avoid a pucker) which would affect the embouchure. If a musician can watch someone eat a lemon without the automatic urge to pucker then it would have no effect at all.
Personally I could watch someone suck a lemon all day and have no problems, but I do smile and laugh easily so I could be distracted by something funny enough.
Not that I ever have to worry about it, my lips haven’t touched a tuba in 19 years.
As my husband the tuba player tells me, the valves are humorously called “spit valves,” but the liquid is very little spit and very much water – it’s condensation, just the same as if you put a water glass over your mouth and blew into it. You blow into a long, spherical piece of brass for a period of time, and sooner or later you’ll have to drain some dew. Pros call them water valves.