Word for not obscure but not mainstream

Is there some way to describe something that the average person doesn't know about but is still not obscure? Such as a musician who doesn't get much radio play but still has thousands or even millions of fans, or how an independent movie that does well at a festival like Sundance but doesn't get a major release.

Solution 1:

Niche

(Adjective). Denoting or relating to products, services, or interests that appeal to a small, specialized section of the population:

• other companies in this space had to adapt to being niche players
• a niche show that ran on late-night television
• the video game industry is no longer niche.

— Oxford Dictionary

Solution 2:

Recondite:

Of a subject or knowledge - little known by the layman or in the mainstream of received wisdom or knowledge. (Oxford Dictionary)

One might write, for example, that intellectual property law (patents, trademarks & copyrights) is a recondite subject matter for many lawyers.

In the alternative, I propose the word fringe

Fringe:

adjective, not part of the mainstream. (Oxford Dictionary)

So, one might say, for example, that the little known playwright has had his work performed to fringe audiences Off-Broadway and at fringe gatherings at the Edinburgh Festival.

Solution 3:

Alternative is a possibility. While it can be somewhat vague and may or may not fit the questioner's needs depending on the context, it is often used to describe an option that's not the most common one but may nonetheless be well known, as in "alternative music" or "alternative medicine".

Solution 4:

Underground

ODO

ADJECTIVE

• Of or denoting a group or movement seeking to explore alternative forms of lifestyle or artistic expression; radical and experimental:
  the New York underground art scene
  wikipedia: Underground Music

Underground can be applied to many forms of media, in contrast to more specific terms such as

• avant-garde art
• experimental , "experimental jazz"
• alternate , "alt rock"
• independent - the connotation is more about how it is funded than its popularity, but non-mainstream funding usually implies non-mainstream popularity

Solution 5:

Indie

1: one that is independent; especially : an unaffiliated record or motion-picture production company
2: something (as a record or film) produced by an indie

"Indie." Merriam-Webster.com. Merriam-Webster, n.d. Web. 28 Aug. 2016.