It tends to be something which has been planted subconsciously in the brain by a mention here, Ruth: more often than not, it won't be an instantly recognisable bit, either, causing some scratching around in the recesses. Today I've had a tiny insistent three chord phrase on strings running through my head: oddly modal. It's only when it joined up with a fragment of piano that I realised it was part of the bridge passage in the Khatchaturian Piano Concerto's first movement.

It tends not to be whole themes but those wonderful little ear-wormy phrases: masses of Tippett bits, and at the moment, since we've been discussing him, three or four works by Martin Butler (a contemporary composer whose music plugs straight into my brain, and a man not exactly unknown to these boards).  Most of the time I can identify straight away: but it's really frustrating when you can't quite place where a tenacious phrase hails from.

Good idea for a thread, Ruth.  Like Ron, my music on the brain tends to come via the indirect sub-conscious route, rather than something  I`ve recently heard. The other day it was a song from The Mikado which I did not want in my head, but it wouldn`t go away.

The same thing happens with words. I will wake up with a word stuck in my brain. Yesterday it was `palimpset`. I have no idea where it came from

Strina - one of the most frustrating things to get stuck on the brain is something that's technically difficult and challenging.

If any part of the Missa Solemnis gets stuck in my mind, it's generally the second (fast) half of the 'Et vitam venturi' fugue, which is one of those infuriating choral passages which ties the brain in knots even in performance, especially when you've been planted in the middle of a large unwieldy choir to keep the damn thing going.  One of these days, perhaps I will have the good fortune to sing it in a choir whose every member is perfectly capable of singing that passage.  This, perhaps, would leave me with a memory of clear semiquavers. Until then, I'd prefer not to have it on the brain  

I bow before the Master, Bryn. I leart it all from yo

I haven't read it, but Ron Dough's already used the term "earworm" earlier in this thread.

Of course, some people call them Leitmotifs and use them as the basis for their entire compositional career

Right now it's lots of songs from Carousel (as I'm spending my evenings playing in a pit).

Generally, I quite often find "The Thieving Magpie" in there.

Oh, and just then, unbidden came the Horn call from Brahms 1st symphony last movement (before it goes allegro).

Tommo

I have now moved on to "Above measure is the pleasure", Juno's bonkers little aria from the last act of Semele.