A phenomenon observed this weekend at Towersey, which we christened 'St Cecilias' Law':~

A session will only play the tunes you know if you don't have your instrument with you,

with the extensions:~

a) if you do have your instrument with you, they will only play the tunes you know when you are at the bar.

and b) If you do have your instrument with you and want them to play a particular tune you wish to learn, they will play that set whilst you are in the loo and unable to hear.

Any others you've observed???

LTS