When musical legends tour in their twilight years, it's usually under sad, financially desperate circumstances—or to promote a new (usually mediocre) album. As keyboardist for Booker T. & the MGs (the house band for Stax Records), Booker T. Jones helmed one of the tightest soul units ever. Their verve and funkiness endure on his vital new disc, Potato Hole, on which Drive-By Truckers and Neil Young back sexagenarian Booker and his expressive Hammond B3. Even the "Hey Ya" cover smokes. (Triple Door, 216 Union St, 838-4333. 7:30 pm, $25 adv/$30 DOS, all ages.)