Call it Stump the Bass Player. Dana McCarthy, bassist at an open mic jam in Acworth, had never heard the pop song a particular guest vocalist requested. Neither had the rest of the band.

The singer described the tune, and the group soldiered on, digging deep and striking gold with a groove all its own. When they were done, the vocalist turned to the band with a beaming smile.

“She told us it wasn’t even close to what the song sounds like,” McCarthy said, “but she loved our version. She said she might even keep performing it that way.”

Magical musical moments like that often come to melodic life at open mic events.

Whether you’re jonesing for the spotlight or simply want to watch from the crowd, Atlanta has no shortage of plug-and-play showcases.

Eddie’s Attic

Long before Simon Cowell uttered his first jab on “American Idol,” local and national singer-songwriters often set their sights on the Songwriter’s Open Mic competition at Eddie’s Attic. Familiar names, including John Mayer, walked away with honors back in the day. And every Monday performers still take the stairs leading to the venue’s showroom in hopes of climbing the ladder of success. Both singer-songwriters and full bands can sign up online for one upcoming Monday night slot at a time. Players must pay an initial $4 sign-up fee, and larger acts pay $3 per additional member. The event typically draws a crowd that tips back libations and nibbles on burgers and more while the musicians do their best. A total of 17 to 19 contestants have 10 minutes to perform a pair of original songs. You’ll typically see plenty of folks wielding acoustic guitars, yet Eddie’s does allow groups with as many as three members armed with a variety of instruments, including scaled-down drum kits, handheld percussion and keyboards. All of the music happens live onstage; no backing tracks here. A panel of judges picks three finalists, each of whom return to the stage and crank out one more song. The judges whittle it down to a winner based on songwriting, playing ability, vocal performance, audience reaction and stage presence. That winner then delivers an encore. Each weekly winner scores an invitation to one of the biannual Shootout contests, which happen Thanksgiving weekend and again on the first Saturday in June. Shootout winners take home a $1,000 cash prize.

7:30 p.m. Mondays. $5 advance; $6 at the door; $25 reserved table for four. Bi-Annual Songwriter’s Open Mic Shootout 39: 7 p.m. Nov. 23. $20 advance; $25 at the door; $100 reserved table for four. 515-B N. McDonough St., Decatur. 404-377-4976, www.eddiesattic.com.

Eddie Owen Presents at Red Clay Theatre

Owen, the former owner of Eddie’s Attic, originated its competition and has been operating a music venue out of the 260-seat Red Clay Theatre since late 2011. Although he brings in local and national touring acts, it only made sense that he’d offer his own Songwriter’s Open Mic event on Mondays. Contestants can choose a date and sign up online. The contest basically hits the same logistical notes as its forefather: as many as three performers at a time, and 10 minutes and two original songs per act. Some differences include the fact that performers get in free and have access to a baby grand piano onstage. Again, judges narrow the competitors down to three finalists. The winner of each weekly event pockets $100 along with a spot in one of Eddie Owen Presents’ own biannual Shootouts, which each offer a $1,000 prize and take place Nov. 29 and the first Saturday in June.

7:30 p.m. Mondays. $5. Bi-Annual Songwriter’s Open Mic Shootout: 7 p.m. Nov. 29. $20-$23 advance; $25-$28 at the door. Red Clay Theatre, 3116 Main St., Duluth. 404-478-2749, www.eddieowenpresents.com.

Dixie Tavern

This open mic experience blends jam sessions with band auditions at the popular live music spot. Chords begin ringing out at 9 p.m. each Monday on a first-come, first-served basis. Musicians, vocalists and full bands can sign up to play. A host band, featuring Barry Richman on guitar, Renard Clark on bass and Bill Diehl on drums, gives musicians and vocalists the chance to delve into everything from country and heavy metal to blues and acoustic singer-songwriter tunes. This means the band must stay on its toes by jumping genres, which Richman said keeps him fresh. The hodgepodge of participating musicians also makes this a potentially fruitful networking opportunity for players. Full bands hoping to land a gig at the club that helped launch Zac Brown’s career can do 20-minute sets. All of the instruments are up for grabs, although Richman said guitarists often prefer to use their own amps and pedals. Dixie Tavern doesn’t have a house keyboard rig, so keyboardists should bring their own. Richman gives sound man Rick Brumley big props for creating concert hall sound. That could be one of the reasons Brown and his bandmates swing by periodically for the open mic jams.

9 p.m.-1 a.m. Mondays. Free. 2319 Windy Hill Road, Marietta. 770-690-0090, www.dixietavern.com.

Locals Bar & Grill

Open mic jams amp up twice a week at this nonsmoking watering hole and bar grub haven. Seasoned musicians hold down the fort in the host bands. Sunday night’s group and the visiting musicians typically lean toward the bluesier side, while the song selection runs a much wider gamut on Tuesdays. Players and singers drop in and out throughout the evening. Performers often pack the stage, and they’ve had as many as nine musicians onstage at a given time. Dana McCarthy, the bass player in the Tuesday host band, said their skills are put to the test each week. Whoever tackles lead vocals typically offers up a few songs in their repertoire, and the band and the singer choose a tune. You might hear a jazz standard one minute, a blast of hard rock the next. It gives musicians a chance to not only play certain music for the first time, but to collaborate with a rotating roster of talent. According to McCarthy, this jam isn’t reserved for the elite. All skill levels are welcome, and he said the band makes sure everyone gets a chance to turn it up to 11.

7-11 p.m. Sundays; 8:30 p.m.-midnight Tuesdays. Free. 5399 Bells Ferry Road, Acworth. 770-627-5121, www.localsbarandgrill.net.