Amper, a startup that offers AI-powered music composition, is announcing that it has raised $4 million in funding.

The round was led by Two Sigma Ventures, with participation from Foundry Group, Kiwi Venture Partners and Advancit Capital. Amper previously raised funding from Brooklyn Bridge Ventures.

You might not expect a film composer like Drew Silverstein (who founded the company with Sam Estes and Michael Hobe) to create a product that ostensibly competes with his own work, but Silverstein doesn’t see that way.

Instead, he pitched Amper as a fast, affordable and royalty-free way to create the music for more “functional” projects (like commercials a or short online videos), where most companies would currently use pre-written stock music. Silverstein said he’s been approached about these projects in the past but found that “the economics just don’t work” — the budgets just aren’t big enough to justify creating new music.

“One of our core beliefs as a company is that the future of music is going to be created in the collaboration between humans and AI,” he said. “We want that collaborative experience to propel the creative process forward. If we’re going to do that, we have to teach computers to be intrinsically creative.”

There are other companies offering AI-driven music composition, such as Jukedeck, which won TechCrunch’s Startup Battlefield just over a year ago. But in Silverstein’s view, this creativity is one of the things that makes Amper unique.

He acknowledged that we’re “not yet at the point where novel, groundbreaking ideas come from machines.” What Amper is good at it, in his view, is collaborating with humans.

Specifically, to create a music track on Amper, you just specify the mood, length and genre that you’re looking for. You can get an initial composition back in just a few seconds (the creation time gets longer as the music you’re asking for gets longer), then you can refine it, for example by adding or removing certain instruments.

Amper is also launching an API today that Silverstein said will help the company to create music at a larger scale by allowing “anyone to power their software their platform or their tool with the creative brand of Amper.”

But how good is the music? You can listen for yourself. I’ve embedded a sample track below, and there are more on SoundCloud.