lah
Concise Oxford English Dictionary © 2008 Oxford University Press:
lah /lɑː/ (also la)
▶noun Music (in tonic sol-fa) the sixth note of a major scale.
■ the note A in the fixed-doh system.
– origin ME: representing (as an arbitrary name for the note) the first syllable of L. labii, taken from a Latin hymn.
'lah' also found in these Oxford entries:

