Jazz clubs usually bring to mind dim lights, linen tablecloths and softly clinking martini glasses, not to mention steep cover charges and/or pricey two-drink minimums. Houston has plenty of those places. But jazz has another side — a spontaneous, free-swinging and earthy one — and there's no better place to see this than King Biscuit's no-cover Tuesday-night jam sessions. Some of Houston's best players descend on the homey Heights bar and cafe not for the money (but please tip), but for the sheer thrill of improvisation and collaboration. Before it got all cultured and highbrow, jazz was party music, and here it still is. But if it makes you feel better, go ahead and order that Manhattan.