Price: Free Operating system requirements: iOS 8.0
Price: Free Operating system requirements: iOS 8.0. Popular Science

We may earn revenue from the products available on this page and participate in affiliate programs. Learn more ›

If you’ve ever been behind the mic at a karaoke bar, you know the agony of a senseless backing track. Slow down your tempo for dramatic effect and the track blindly rolls forward. Speed up and the track stubbornly lags. Creative freedom is lost.

For decades, classical musicians have wrestled with the same problem. Many of them practice solos against backing tracks, and the inability to modify tempo can limit their creative expression. Cadenza, an orchestral accompaniment app developed at Harvard Innovation Lab, aims to change that by listening to soloists as they play and syncing the tempo of the backing track to them.

At the heart of the software, Cadenza uses pitch analysis to track where a musician is in the melody line and how his or her speed has changed in preceding measures. The algorithm uses that information to predict how the musician will play in upcoming measures.

“It brings a full orchestra into the study [room],” says Nicholas Kitchen, who plays violin in the Borromeo String Quartet and has recently started using Cadenza with students. “As a teacher, there is just layer upon layer being added to the learning.”