The pianist Robert Taub was puttering around the house one afternoon in 2004 while his teen-age daughter was practicing for a violin lesson  a Schubert sonatina in A minor. His assessment of her playing was diplomatic: “She needed to be reminded about notes and rhythms.”

What followed was a brainstorm that explains why Mr. Taub  who made his reputation playing two distinctly different B’s, Beethoven and Milton Babbitt  has put his performing on hold, and why “software entrepreneur” now tops his résumé.

“I thought, wouldn’t it be wonderful if she could take a photograph of her page of music and hear it instantaneously,” he recalled. “She’d know what the right notes are, and what the right rhythms are, and she could imitate what she heard.”

Soon he was dreaming of a device  or maybe just software running on a computer  that could do everything he had learned to do in music theory class: read and play a printed musical score, and listen to a passage of music and transcribe it, down to the key signature, the tempo and the time signature. He said that a quick check showed that nothing then on the market could do all that.