We are a fanbase that actively writes music ABOUT the show (and in many genres and in many different ways). I wouldn't consider a person who is a fan of the show but who doesn't do anything with pony images, titles, or MLP-themes a "brony musician" and i don't think most people use that in that way. But some people who sometimes say they aren't brony musicians title their tracks with character names, use pony images, and then hang out in the community and yet don't want to labeled as part of us; and thats really disengenuous.
We allow a lot of flexibility when it comes to brony music you can do any genre, you can do instrumentals, all that we ask is you find some way to channel some influence of the show. Just being a fan of mlp and making non affiliated music doesn't really make you a "brony musician". I think we know that and yes we benefit as much as we limit ourselves when we take that on. There's a load of people just waiting to give your music a chance if it just captures some of that MLP magic.
There's been a few people like Swagberg, Renard, Ken Ashcorp who've done 1 or 2 pony tracks. I wouldn't call them "Brony Musicians" anymore than I would call Queen, Rolling Stones, Kiss, Rod Stewart a "Disco Band" that did 1 or 2 disco songs in the 70's. But they COULD be lumped in with us/them if you wanna include making a well known brony/disco song in the most generic sense or more importantly in the past tense. They still made an impact as a one-hoof wonder and there's a lot of people who make a pony track or 2 and disappear forever from this community.
As a "brony musician" as you are combining 2 things - music and MLP as the subject. For awhile people were equally calling it "pony music" but that sounds a little weird to the outside world so brony musician or brony music stuck. When you don't combine those 2 interests you're not a "brony musician" you're "a brony who happens to be a musican". Andrew WK doesn't make "pony music" and is not a "brony musician". He's a musician who happens to be a fan of MLP. See what I'm saying?
People can come and go and make pony music and then decide not to make it at a different point in their lives. It doesn't stop what they've done (Archie **cough* Icky *cough*) but it may change how they choose to identify themselves in the present tense. Certainly a lot of our eldest and most well known musicians have indeeed moved on and don't make brony music anymore.
But don't be embarassed to be a PART of our community as MLP is a show that has HUNDREDS (if not one THOUSAND plus over 2 years) of people making dedicated music about it, that has its own massive fanbase, that has about plenty of dedicated radio stations playing NOTHING BUT pony music, that has blogs that get hundred and thousands of hits a day highlighting that music, that has several conventions dedicated to that fanbase, it's own musician forum (mylittleremix), and it's own compilations and events. I'm a guy who runs a directory just to help brony musicians be found and stick out from each other because that's actually needed. That's a big fanbase.
But a label isn't something that shouldn't restrict or embarass anyone! There's no reason to feel that!! It's just simply means "hey there's a person who made some music about mlp" and that's because you did (and likely several times!). What we share in this community may not be that unique. What's important is how you create your own story about who you are as a person outside of that and what makes you different and unique. Just because we share a lot in common doesn't mean we're all the same, we're not. It's great to be linked as brony musicians but we're all different in the many ways we make music and live our lives. This music community is still built up of hundreds of individuals just trying to tell the stories of who they are through their unique contributions, personalities, pasts, and styles. And that's awesome, that's as it should be. It's great to be different but it's wonderful to have shared interests.