Aggie Theatre: 204 S. College Ave., Fort Collins, 1-970-482-8300. Fort Collins's biggest live-music hall is a converted movie theater retrofitted with two bars. The Aggie sports a broad, multi-leveled floor that ensures a good view from anywhere, although a brutal chain-link fence separates the aged from the underaged.
Alley Cat: 1222 Glenarm Pl., 303-571-4545. If you want to get your groove on at Alley Cat, you'd better have plenty of scratch. Sharing the building with Diamond Cabaret means that at the Cat, the hotties and the drinks are high-dollar. So dress like you mean it.
Avogadro's Number: 605 S. Mason St., Fort Collins, 1-970-493-5555. Offbeat and off the beaten track, Avogadro's Number's warmly lit, non-smoking stage area is painted with a stunning mural that circles the room with people, stars and planets. The crowd reflects the folksy, friendly vibe of the music calendar: lots of bluegrass acts, jam bands, acoustic guitarists/singers and a solid open-mike night.
Ayja: 7800 E. Hampden Ave., 303-694-4898. A 180-degree turn from its regular incarnation as Proof of the Pudding, the Wednesday-night Ayja (pronounced "Asia") brings a bit of SoHo-meets-Far-East glitz. With a throbbing dance floor, pricey drinks, not-so-pricey sushi and a see-or-be-seen crowd, the place is almost too hip for its own good.
Bash: 1902 Blake St., 303-298-7994. This big brick warehouse has undergone a complete renovation. The new silvery and sparkly artwork contrasts nicely with Bash's dark interior, a perfect setting for many larger-than-you video screens and hot DJ mixes.
Beyond: 500 16th St., Denver Pavilions, 303-623-9663. Beyond the cool black depths of the lobby and the hallway, the dance floor at Beyond gets hot -- sometimes too hot. When that happens, patrons can chill in the Ice Room, the club's transformed walk-in freezer, where shots are served to the sweaty before they venture back into the double-bass multimedia blast of the Pavilions' latest nighttime heat wave.
Blondie's Firehouse: 180 S. Union Blvd., Lakewood, 720-963-8408. The people at Blondie's take their theme seriously, hanging a fire suit and other memorabilia from the ceiling and cheesecake pictures of fire guys and gals in the bathrooms. Live-music Friday centers around pop and classic rock, but the rest of the week it's pretty much all karaoke, all the time.
Blue 67: 1475 Lawrence St., 303-260-7505. The decor at Blue 67 is as exciting as the martini menu, with arty square booths and little geometric couches that fill the very blue LoDo space. Large windows and a patio facilitate easy people-watching, while electronic and fusion DJs, and jazz on Wednesdays, command the Euro-chic crowd nightly.
Blue Ice: 22 S. Broadway, 303-777-3433. The thick blue drapes in the window suggest a martini bar, but Blue Ice is more of a drinker's den than a fashion haven. Tuesday night's jazz-jam sessions are similarly open and non-elitist, and the club's mid-Broadway locale means over-imbibers can still catch a bus after closing.
Blue Mule: 1624 Market St., 720-932-6853. The Blue Mule has quickly established itself as a reliable spot with a solid music calendar. The subterranean Mule books familiar and up-and-coming artists from the local rock realm.
Bluebird Theater: 3317 E. Colfax Ave., 303-322-2308. Built in 1917, the Bluebird Theater has a history of intimacy: Before its renovation as a music venue, it was a porn theater. Now one of the city's finest small-room concert halls, the club is a happy marriage of arresting architecture and forward-looking music. Touring acts and local bands get equal stage time under the ´bird's wing, where cherubs look down from vaulted ceilings onto hipster congregations.
Bottoms Up Tavern: 3124 S. Parker Rd., Aurora, 303-695-4711. Newbie musicians might try to take refuge in the thick black curtains that flank the large stage at Bottoms Up Tavern. A kind of starter bar for the live-music set, the Aurora venue gives both green and seasoned performers in all genres their moment in the spotlight. The music can be uneven, but the drinks are consistently cheap and the crowd is friendly, casual and forgiving.
Boulder Theater: 2032 14th St., Boulder, 303-786-7030. The artwork on the walls in the Boulder Theater is enough reason to visit the historic movie-palace-style venue, where film screenings now take a second seat to first-rate music performances from local and national acts of all genres. A stellar annual jazz series, monthly tapings of the nationally broadcast e-town radio program and a comfortable bar elevate an already elegant room.