If you listen to classical radio, eventually you'll hear something like: "Here's a divertimento, number 136 in the Koechel catalog of Mozart's works." Who or what is Koechel? Ludwig Koechel (Ludwig von K?chel) was an amateur musician in 19th century Austria who had a thing for Mozart. He set out to track down what all Mozart wrote and arrange it all by date of composition. Koechel's "catalog," published in 1862, was the first systematic index of any European composer's music. It ran from a tiny childhood harpsichord piece of Mozart's, K. 1, up to the Requiem Mozart was working on at the time of his death, K. 626. Koechel got an impressive amount right - but not everything. He assigned numbers to a few pieces that weren't really by Mozart; he left out a few pieces that really are; and more importantly, not every work was - or could be - dated correctly. In "K is for Koechel," Mozart scholar Neal Zaslaw and his daughter, Sarah Zaslaw of GPB, explore how Koechel got as close as he did and what we know now that Koechel didn't. Along the way, they look at myths of genius, how Mozart really composed, the ways later scholars tinkered with Koechel's chronology, the formula connecting K numbers to Mozart's age, modern forensic Mozart sleuthwork from paper dating to handwriting analysis, and plans for the forthcoming New Kochel Catalog. And beyond the talk, there's plenty of time in the hour for what makes it all matter: Mozart's music.