Oh, how far we've come. It wasn't long ago that phones were just used for talking. Now people can blow into their Apple iPhones and actually play Amazing Grace. They can do so by playing the Ocarina, one of the hottest iPhone apps to come out recently, despite the fact that it costs $1.

Launched last week, the Ocarina has already climbed to the top of the charts in iTune App stores in France, Denmark and Spain, said Smule founder Jeff Smith.

Smule is the developer of the app. The startup formed this summer with $1.6 million in funding from Bessemer Venture Partners, Maples Investments and angel investors, said Smith. The Ocarina is the fourth app, and the number of downloads has already broken six figures, said Smith.

I bumped into Smith at the Under the Radar conference this week. It's not typical to have an executive play you a tune at a conference. But Jeff played one for me. In fact, we heard from people around the world playing the Ocarina. One person, was, in fact, playing Amazing Grace. (In this video interview, Smith - who was pursuing his doctorate in music before starting Smule - demonstrates his musical abilities.)

Smule allows people to "express themselves in sound and engage with one another through sound," said Jeff.

Why did you start charging out of the gate? I asked, referring to the fremium model that many companies typically embrace. "Free is great," he said. "For us, we're interested in making money." That said, there is room for advertising on these apps. Smith believes he can charge CPMs north of $4. 

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