If Russian hackers were to break into Mitch Joel's telephone and browse through his emails, they'd be surprised at what they found. Sure, there would be messages from the clients and executives at Mirum, the digital agency Joel founded and grew into 45 countries and 2,200 employees. There would also be invitations from companies like Google, Starbucks and Wal-Mart to talk to them about digital marketing. And there would probably be some emails from his publishers about his bestselling books.

But in between that work stuff, there would also be emails from Chuck Rainey, Liam Wilson and Tim Lefebvre, saying that they were in town and inviting him for a coffee and a chat. That's because when Joel isn't talking to audiences and building marketing campaigns, he runs a podcast that aims to build the largest oral history of bass players. Through No Treble, Joel has spoken to just about all of the world's greatest bass guitarists, pulling out their stories and chatting with them about life on the road.

"This podcast has given me the chance to speak with everybody," he says. "It's given me tremendous access to these people whose stories haven't been told."

The result has been not just a growing account of the music industry told from a unique angle and about one particular instrument, but also a powerful business lesson in the value of micro-niching. There's no shortage of blogs and podcasts about music in general and guitars in particular, and even a few about bass guitars. But by focusing on just one aspect of just one kind of instrument and the people who play it, Joel has managed to create a product with a dedicated audience.

Finding that micro-niche isn't simple but the best guide is your own interests. Joel isn't a bass player himself, though he did learn to play before realizing that he preferred writing about music than strumming on stage and spending his days traveling from gig to gig. The inspiration for No Treble came from his realization that other interviews would focus on the musicians' albums and their gear while he wanted to know who the bass players were and what they did.

"I want to read about them the same way that you would hear a story told about them," he says. "I wanted to know what makes them as artists creative, inspiring and interesting. I wasn't getting that anywhere."

There are few areas of interest more crowded than the music industry. But Joel made his podcast a success by not thinking about success at all. Instead, he thought about what he wanted to hear and assumed that other people would want to hear about it too.

It also helped that he was doing it for fun. The No Treble podcast is a labor of love, and regardless of the size of the audience, Joel loves putting it together and talking to people whose music he so admires. Focus on your own personal interest, do what you enjoy and not only will you have a great time, you'll also have a better chance of creating a great product. And your inbox will be a lot more interesting too.

Listen to the entire interview with Mitch Joel on the FUN podcast.