One Steve Limit/Music

Inversions of, and exceptions to, a One Steve Limit in Music include:

When Kevin James LaBrie joined Dream Theater, he dropped his first name and adopted James as his stage name, to avoid having two Kevins in the band (along with Kevin Moore). The band still had two Johns, however.
Deep Purple has had multiple singers, but the best known is Ian Gillan. The drummer is Ian Paice.
And Our Lady Peace frontman Michael Maida became Raine Maida to avoid confusion with guitarist Mike Turner (and possibly just to be more memorable.)
Progressive metal band Symphony X has three Michaels: Michael Romeo on guitars, Michael Pinnella on keyboards and Michael Lepond on bass guitar.
Extreme metal band Dimmu Borgir once had three Stians: Stian Thoresen (vocals, better known as Shagrath), Stian Arnesen (bass, better known as Nagash) and Stian Aarstad (keyboards, no stage name).
The Mike Doughty song "27 Jennifers" plays with this trope:

I went to school with twenty-seven Jennifers
Sixteen Jenns, ten Jennies and then there was her.

- This is almost certainly based on a real phenomenon - witness this college newspaper comic from 1990...
The core members of They Might Be Giants are John Flansburgh and John Linnell. They are often referred to by fans as "the Johns." For almost five years, their touring band of Dan Miller, Dan Hickey, and Danny Weinkauf was often called "the band of Dans." In 2004, Dan Hickey was replaced by Marty Beller, introducing a third name to the group.
Australian Pink Floyd introduce themselves on stage as six Bruces, four Sheilas, and Rolf.
When Long Island band Taking Back Sunday replaced their lead guitarist and back-up vocalist for the second time, they ended up with two Matts, Matt Rubano on bass and now Matt Fazzi on guitar. They differentiate by last name.
The Rodney Carrington song "Fred's Riding Fred" parodies this, as the narrator is drunk and can't remember the names of anyone in the story, so he names them all Fred. This includes the protagonist, the horse and the protagonist's girlfriend.
Helloween has Michael Weikath and had Michael Kiske. Weikath is frequently referred to as "Weiki" and Kiske is occasionally "Michi" (though "Michi" seems to be more a fangirl thing).
Partial example/subversion with Alice in Chains. The band had two bassists named Mike, but not at the same time.
Relient K has Matthew, John, Matthew, Jon, and ~~Matthew~~ ~~Dave~~ Ethan.
The Academy Is... has Mike Carden (rhythm guitar) and Michael Guy Chislett (lead guitar). Before Chislett joined the band, the very first lineup included Mike Carden and Mike DelPrincipe (drums).
The Cab has Alex De Leon, Alex Marshal, and former member Alex Johnson.
Lacuna Coil has two Marcos, two Cristianos and a Cristina... and Andrea.
Placebo are a bit confusing with this, in that they replaced a drummer named Steve (Hewitt) with a drummer named Steve (Forrest). Also, the bassist's name is Stefan.
Led Zeppelin had a John (Bonham) and a John Paul (Jones). They did not have a John Paul George Ringo, however.
The Tea Party had two Jeffs (Martin and Burrows).
The Beatles had lead guitarist George Harrison and producer George Martin, which can lead to all sorts of confusion when you're reading about the production of certain albums.
Bruce McCullough from The Kids in The Hall had a song called "Daves I Know", each verse being about a different Dave (or David) from his life.
Marillion has two members actually named Steve: lead singer Steve Hogarth and lead guitarist Steve Rothery. They are often referred to as "h" and "Rothers" respectively to avoid confusion.
Def Leppard have two "Rick"'s, Rick Allen, the drummer, and Rick Savage, the bassist. Rick Savage is differentiated by the nickname "Sav". (Interestingly enough, they also had a "Steve", rhythm guitarist Steve Clark, who died in 1991.)
Australian band Powderfinger includes two Johns. One goes by JC, which doesn't really help since the other's surname also begins with C.
Averted by the short-lived supergroup GTR, featuring progressive guitar heroes Steve Howe and Steve Hackett.
Also, in the band Toto, guitarist Steve Lukather and keyboardist Steve Porcaro.
When he formed Dexys Midnight Runners, Kevin Rowland insisted that Kevin Archer (the group's first guitarist) start going by his nickname "Al" Archer. Apparently, he even said, "There's only room for one Kevin in this band."
The Brechtian cabaret band The Tiger Lillies consists of Martin the Evil Clown lead singer, and two guys called Adrian.
From about 1995 to 2008 Nocturnal Rites had both Nils Norberg and Nils Eriksson in their line up. Norberg used to sign his autograph as "Nils2".
Danish pop band Alphabeat has six members: Anders, Stine, Anders, Rasmus, Anders, and Troels.
During their peak, Duran Duran had three members all with the last name Taylor. Not one of them was in any way related to either of the other two.
Devo has both Robert Mothersbaugh and Robert Casale. They are generally referred to as Bob1 and Bob2.
Jon Anderson left Yes in the late 70s and Trevor Horn took his spot for the album Drama before the band went on hiatus. When they reformed for 90125, Anderson returned as vocalist, but Trevor Rabin became their new guitar player, and Horn produced the album.
Kevin Crompton (Cevin Key), Kevin Ogilvie (Nivek Ogre), and Dave "Rave" Ogilvie of Skinny Puppy.
Journey has/had three Steves: Steve Perry (lead singer), Steve "Smitty" Smith (drummer) and Steve Augeri (lead singer following Perry's departure from the band.
The original lineup of Pink Floyd technically had two Rogers, but it wasn't much of an issue because Roger Barrett was already going by Syd before the band started.
US thrash metal band Whiplash is an odd example as one of their Rock Trio lineups had two Anthonys and one Tony, but they all performed as Tonys.
The Spice Girls had two Melanies. Melanie B (Scary Spice) and Melanie C (Sporty Spice). The initials remained in their stage name as they started solo careers, although Scary was simply known as Mel B.
Vocaloid has both a Miku and a Miki.
The Eagles have Don Henley and Don Felder.
REM has both Michael Stipe and Mike Mills.
Sound Horizon's Roman takes the aversion to the logical extreme, where just about every male character is named Laurant.
Paul and Storm have some songs supposedly by a barbershop quartet entirely made up of guys named "Barry". The fake band is called "The BarryTones".
Insomnium's original lineup consisted of Niilo Sevänen (vocals and bass), Markus Hirvonen (drums), and two guys named Ville on guitar. After Ville Vänni left the band, leaving Ville Friman as the only "Ville" in the band, his replacement was...another Markus.
Canadian band Martha and the Muffins (of Echo Beach fame) was named for singer Martha Johnson, but they also had keyboard player Martha Ladly during their successful period in 1979/80.
An early line-up of Whitesnake featured drummer Dave Dowle, known as 'Duck' to distinguish him from David Coverdale; he was soon ousted in favour of Coverdale's old Deep Purple mate Ian Paice.
- The most recent line-up includes two Brians: drummer Brian Tichy and keyboard player Brian Ruedy.
Kiss guitarist Ace Frehley's real first name is Paul; he used his nickname of 'Ace' to distinguish himself from Paul Stanley (who, ironically, is not a Paul at all. His real name is Stanley Eisen.) For similar reasons, Paul Caravello changed his name to Eric Carr upon joining the band as drummer.
Lampshaded by The Donnas who went by the names of Donna A, Donna R, Donna F and Donna C until reverting to their own names by their fourth album.
For a short time in 2010 Evanescence featured two members called Will Hunt, both drummers. Vocalist Amy Lee dubbed the 'new' one Will 'Science' Hunt during his time with the group.
Finnish power metallers Stratovarius (known for their tendency to be a Revolving Door Band) featured guitarist Timo Tolkki and vocalist Timo Kotipelto for several years until the former quit the band.
The Faces featured bass player Ronnie Lane and guitarist Ronnie Wood, the latter now better known as a Rolling Stone.
Two out of the three Beastie Boys are named Adam. They're usually credited by stage names anyway - Adam Yauch is MCA while Adam Horovitz is Ad Rock.