He is the Paul Tietjens Professor of Music at Washington University in St.
Decker was graduated from Fresno Pacific College in 1989, then earned a Master of Music degree in harpsichord from the San Francisco Conservatory of Music in 1991.
[1] In 2019, Decker testified as an expert witness in a lawsuit against Katy Perry, stating that Christian rapper Flame produced a "unique" eight-note ostinato — a repeating sequence of musical figures within a song — which Flame's legal team claimed Perry plagiarized.
[3] US District Court judge Christina A Snyder said "It is undisputed in this case" that the ostinato was "not a particularly unique or rare combination.
"[4][5] Music theorist and YouTuber Adam Neely criticised Decker's arguments as "intellectually dishonest", and claimed that Decker had "sold us all out" with his involvement in the case.