Marcus Belgrave, a trumpet and fluegelhorn player who worked with Ray Charles, Charles Mingus, Max Roach and others before settling in Detroit in the early 1960s and becoming a coach and conscience for that city’s jazz scene, died on May 23 in Ann Arbor, Mich. He was 78.

His wife, the singer Joan Belgrave, said he died of heart failure, the result of chronic obstructive pulmonary disease, at Glacier Hills, a care and rehabilitation center.

In one way or another, Mr. Belgrave was mentor to many of Detroit’s greatest jazz musicians over the past 50 years. They include the pianist Geri Allen, the saxophonists Kenny Garrett and James Carter, the violinist Regina Carter, the bassists Rodney Whitaker and Robert Hurst and the drummers Karriem Riggins and Ali Jackson.

In the early 1970s, as the live jazz scene in Detroit shrank and Motown Records, which had given work to Mr. Belgrave and many other local musicians, decamped for Los Angeles, he became involved in teaching opportunities that had grown out of antipoverty programs instituted under President Lyndon B. Johnson.