Tegan and Sara

Tegan and Sara Quin have been playing music professionally long enough to have long since moved on from their folk-rock days (they played one of the Lilith Fair tours -- remember those?) and to develop a distinctive chamber-indie-pop sound. The twin sisters from Calgary, Alberta, have been playing long enough to tour the world several times, to have many of their songs show up in trendy TV shows (five of them on Grey's Anatomy alone), and to be covered by the White Stripes. They're older than Britney Spears. They're old enough that they were probably already on tour when the guys in Panic! At the Disco were in second grade. They're old enough that one of them is married (well, in a Canadian civil union -- both sisters are gay).

And yet I find I keep having to remind myself that Tegan and Sara are not kids. For starters, there are those girlish singing voices. Then there is the goofy between-song banter and the family stories and silly pop-culture references that come up in interviews. There are all the times their fans refer to them as "girls." And, of course, there are the stylish haircuts.

We all act like younger versions of ourselves when we're around our families. I can only imagine what it does to one's adult sense of self to tour the world for years at a time with an identical twin sister. Eventually, Tegan and Sara will start to look older, sound older, write older. It will be an interesting transition to watch.

TEGAN AND SARA, Spreckels Theatre, Tuesday, October 30, 8 p.m. 619-235-9500. $30.