Startups is a new column about new companies, big ideas and bold discoveries happening in the L.A. area.

Harold Lee was a guitar player who dropped out of music school and found himself handling the marketing for a guitar store chain while he worked toward a business degree. One night, he watched his wife play Guitar Hero and have a great time.

“I just started thinking, why not use a real guitar instead of a piece of plastic?” Lee recalls. An idea was born: to make a mobile instructor that would work with any guitar — and make learning an instrument more like learning a game.

Lee and his team faced a huge hurdle, though, and it had to do with pitch detection.

“Pitch detection for one note at a time is not that difficult — guitar tuners can do it, and so can your ear,” says Lee. “But the tricky part comes when more than one pitch at one time comes from the same instrument, like a guitar.” That's called polyphonic pitch detection, and after scouring the research world for an expert in it, Lee and the company's co-founder, Tyson Butler, found Roger Dannenberg, head of the computer music department at Carnegie Mellon University.

With Dannenberg's help, they tried a new approach. Instead of software that understood all the pitches in the world, the program would evaluate what it heard against the notes it expected to be played — more like a video game and less like a symphony.

Lee supplied Dannenberg with training data: hundreds of thousands of notes played on different guitars, matched up to the target music. Dannenberg trained his algorithms to be tuned across the various guitars, taking input from the actual analog files and comparing those notes with what they were supposed to be.

The result is Rock Prodigy, a mobile instructor in an iPhone and iPad app that can help anyone learn to play guitar. The app is currently 99 cents; inside it, players can purchase lessons for 99 cents or songs for $1.99.

After selecting a song, the user can choose the level of difficulty, then follow the notes on the screen — a cross between sheet music and Guitar Hero.

Rock Prodigy has teamed up with artists to create individual apps geared just for fans — Dave Mustaine of Megadeth has an app that guides users through his songs with his own voice, even telling people how to hold a guitar in order to shred like him.

Guitar is just part of the equation, Lee says. “We have a prototype for piano, using master recordings. Our polyphonic pitch detection works for any instrument, so we envision it for voice, brass, woodwind or strings.”

The culture of innovation and entrepreneurship in Los Angeles has helped the startup to grow and thrive. “The heart of L.A. is absolutely entrepreneurial, and it's very musical. It's a dream, because there's so much music, so much entertainment going on here, which is a glue for that in music distribution and entertainment,” Lee says.

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LA Weekly