"What Is This Thing Called Love?" is a performance of the Cole Porter standard from the 1996 live album Alone Together by Lee Konitz, Brad Mehldau, and Charlie Haden. The 32-bar AABA form in the key of C provides a well-worn harmonic framework that each member of the trio reinterprets with individual distinction. Konitz opens with four choruses on alto saxophone, his improvisation unfolding with the patient, exploratory quality that defined his approach to the Tristano school of jazz, where melody is discovered through deep listening and real-time invention rather than reliance on preconceived patterns. Mehldau follows with four equally absorbing choruses on piano, his solo marked by the rhythmic sophistication and harmonic depth that would soon establish him as the defining jazz pianist of his generation. Haden's contribution is particularly remarkable, stretching to six choruses of bass improvisation at an elevated tempo of 187 beats per minute, an unusually extended statement that demonstrates his extraordinary melodic conception on the instrument. The performance, recorded live at Birdland in New York, captures the trio at full creative stretch, each musician feeding off the others' ideas in a continuous stream of musical conversation. The drumless format places every note under a magnifying glass, revealing the exquisite sensitivity with which these three artists listen and respond.