That happened when I was 15 or 16. A friend at school was a whizz with computers, and got onto "Young Scientist of the Year" (a BBC competition) with a homemade synthesizer. In order to demonstrate its abilities he organised a scratch band to play along with, including me (I was on flute, channelling Ian Anderson). Needless to say, we were pretty rubbish, but it was national television! He went on to be a Cambridge don for his pains.