By Sacha Pfeiffer

In the early 1720s, Johann Sebastian Bach composed a set of Two-Part Inventions to help his eldest son, Wilhelm Friedemann Bach, learn to play the keyboard.

Now, 300 years later, jazz pianist and composer Dan Tepfer has extracted the framework and narrative from these deceptively simple exercises to guide new improvisations for an album he calls Inventions / Reinventions. "The musical content, what's going on underneath the surface is so profound that it's really this wonderful way of introducing children to what the greatest music can be," he tells NPR's Sacha Pfeiffer.

Bach's pieces help the learning pianist master harmony, rhythm and technique. They are called Two-Part Inventions because there are two separate voices distributed between the pianist's two hands. "So not only is there a dialogue between two voices here, but there's also a dialogue between two hands," Tepfer explains.

The New York-based pianist initiated a conversation with Bach across the centuries by emulating the composer's narrative structure: A musical idea, or theme, is like a protagonist, introduced before experiencing various adventures — expressed musically through modulations — and ultimately returning to the home key.

"The chief goal here is to be in conversation with Bach and to stay in my shoes — not to be playing on his turf, but to be using his ideas on my turf, which I think is what any good conversation is," Tepfer says. And in doing so through improvisation, Tepfer is also drawing from the beating heart of Bach's music. The Baroque master was renowned in his own time as an improviser, one people would travel from all over Europe to hear.

It's not the first time Tepfer, 41, has improvised in ways that build upon Bach. In his 2011 album Goldberg Variations / Variations, he played the original 18th century composition (an aria and a set of 30 variations) alongside his own 21st century improvisations. During the pandemic, Tepfer, who also has an undergraduate degree in astrophysics, wrote a computer program that plays back each Goldberg variation, but flipped upside down.

Essentially, Tepfer inverted the multiple lines of music (counterpoint) Bach had composed. Where a melody might fall in the original composition, the pattern would rise in what Tepfer called the #BachUpsideDown project. While the flipped versions are completely new music, they also are an echo of the original piece and sound oddly familiar.

With his new Two-Part Inventions, Tepfer's improvisations are in the nine keys not covered by Bach's cycle. Out of the 24 possible major and minor keys, Bach only composed these exercises in 15 of the most commonly used keys. But Tepfer is quick to insist that nothing is missing from the original compositions.

"I don't believe those gaps need to be filled at all. I never want to improve on what Bach has written. I think it would be foolish to do so," Tepfer says. Instead, he adds, "I suddenly realized that Bach had left open a window for me to respond to him in."

Listen to the full Interview HERE