The audiocassette tape is not dead. In fact, one Springfield, Mo., cassette maker says it has had its best year since it opened in 1969.

"You can characterize our operating model as stubbornness and stupidity. We were too stubborn to quit," said National Audio Company President Steve Stepp.

NAC is the largest and one of the few remaining manufacturers of audiocassettes in the U.S. The profitable company produced more than 10 million tapes in 2014 and sales are up 20% this year.

"Probably the thing that has really enlarged our business at a faster phase than anything is the retro movement," Stepp said. "There's the nostalgia of holding the audio cassette in your hand."

NAC has deals with major record labels like Sony Music Entertainment and Universal Music Group as well as a number of small contracts with indie bands. About 70% of the company's sales are from music cassettes while the rest are blank cassettes.

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"There was a drive from the independent bands to get that warm analog sound again, and it just continued to grow and grow," said NAC Production Manager Susie Brown.

The company still uses machines built in the 1970s in its production lines.

This article originally published at Bloomberg here