He began studying classically at age 7 and discovered his passion for jazz music when attending Interlochen Summer Camp.

There, he met piano prodigy Eldar Djangirov, who made a lasting impression on Diehl through his enthusiasm for Oscar Peterson and Art Tatum.

In 2010, Live at the Players featured two of his trios: David Wong and Paul Sikivie (bass), and Quincy Davis and Lawrence Leathers (drums).

The Bespoke Man’s Narrative (2013), Diehl’s debut album on Mack Avenue Records, reached No.1 on the JazzWeek Jazz Chart[7] and is described as "honest music that invites you back in to discover new wonders with each listening.

Others he has performed with include: Warren Wolf, Lew Tabackin, Matt Wilson, Wycliffe Gordon, the Jazz at Lincoln Center Orchestra and the New World Symphony.