finally looked it up

[lauradi7dw]

I don't know what they sound like, but I am aware of the singing twins Tegan and Sara. I have wondered for a long time whether they were named for the companions of Dr Who (#4 for both, #5 for Tegan) but apparently the singing sisters were born in 1980 and Tegan didn't turn up on the Tardis until 1981.
OK, no more goofing. Back to acids and bases and salts (oh my).