It strikes me that musicians are like computer geeks, in that they often have a fair bit of expensive kit lying around and there is a fair bit of tech involved

It strikes me that musicians are like computer geeks, in that they often have a fair bit of expensive kit lying around and there is a fair bit of tech involved in making and recording good music. So if in addition to showcasing the music, you also let the musicians talk about how they make it, you would both foster interesting conversations about the technicalities of the music and the tools used. That in turn is a perfect place for a marketplace for musicians to connect and buy/sell second-hand items - and a very valuable spot for companies to advertise gear to interested buyers or an opportunity to charge the site's members themselves for posting ads. Also, finding session musicians who can stand in or help with a recording session may be another reason members might want to advertise to each other.