Learn English – What does “play the trumpet” mean

In a recent Academia SE question, user moonman239 writes:

What is proper etiquette for college students needing to leave the lecture room for any reason?

Example: Bathroom breaks, an urgent phone call, or a need to "play the trumpet" (if you know what I mean)

As the user does not seem to respond any more, those of us who do not know what he or she meant are now left wondering what was actually meant.

Based on googling, I did not find any conclusive evidence to a commonly understood meaning of the expression "play the trumpet". In fact, virtually all results I could find seem to talk about people who – literally – play a musical instrument, a trumpet.

I can see some possible explanations that could (remotely) make some sense also in the context of the question, although they realistically strike me as quite far-fetched:

• It might be a general way to express "make noise" (literally and figuratively), by talking, singing, jumping around, or whatever other freedom is desired that would not be possible in the described context (of a university lecture hall).
• Trumpets can be used to play recognizeable melodies, and thus may serve as leading or solo instruments. Hence, "playing the trumpet" could be a euphemism for "taking the lead", for instance, in a group working on a project, as opposed to a lecture hall, where the lecturer has the superior role towards all attendees.

Given that a euphemism is used in the first place, though, it could also be that the expression is meant to refer to a taboo-ish topic:

• If we concentrate on the play part (with the trumpet being a somewhat arbitrary placeholder for the object of playing to create a memorable expression), the expression might be interpreted as a euphemism for "masturbation".
• If we concentrate on the trumpet part, i.e. something that creates loud sounds, the expression might refer to "(audible) flatulence".
• In fact, the direct Chinese translation of "playing the trumpet" ("吹喇叭") seems to be used in Taiwan as a euphemism for fellatio.

With the background in mind that this is about something that could cause students to urgently leave a lecture rather than wait for some one or two hours until it ends, not a single one of these interpretations sounds actually likely (even less so if the activity would require several students to suddenly feel the same need).

Therefore, my question is: What does the expression "play the trumpet" mean (if it means anything), and if so, is it commonly used in English (or just in some English-speaking places)?