Mason Jeffery-Off (b. 2004) is an emerging Canadian double bassist, electric bassist and composer based in Montréal. Originally from Ottawa, Jeffery-Off moved to Montréal at 18 and graduated with a Bachelor’s Degree in Jazz Performance at McGill University in 2026. There, he studied with Ira Coleman and John Hollenbeck. He can be seen performing with Jean-Michel Pilc, Darrell Green, David Binney, Kevin Dean, and has also appeared with the National Arts Centre Orchestra.

At 18, Jeffery-Off was one of 16 international jazz musicians under the age of 25 to be selected for Betty Carter’s Jazz Ahead, a performer-composer residency located at the John F. Kennedy Center for the Arts in Washington DC. In 2024, he received the Hnatyshyn Developing Artist Grant (Oscar Peterson Grant for Jazz Performance). He was also selected to participate in The Banff Centre’s Jazz and Sonic Arts residency in 2026.

Jeffery-Off leads Marvelous Creatures, an ensemble performing compositions that transform the melodic contours of spoken and written language into music. He also leads a trio with Ben Shaw on drums and Sam Fortin on piano performing his original music across Montréal. Jeffery-Off’s work bridges jazz, 20th-century classical music and folk.

Jeffery-Off’s EP ‘Everything Shifts’, was released in September of 2026.