He grew up in Pittsburgh, PA where he studied with guitarist Joe Negri, and in Rochester, NY.

[2] [3] Mackay’s first Drag City release, Esker, was described by reviewer John Mulvey of Uncut "as a neat sampler of his unshowy virtuosity, at once brisk and mellow.

"[4] His arrangement of the Steely Dan song Deacon Blues appeared on the collaborative covers album by Bonnie Prince Billy and Bill Callahan, Blind Date Party (Drag City, 2021)[5][6] MacKay is a member of Black Duck, along with Douglas McCombs (Tortoise, Brokeback) on guitar and bass, and drummer Charles Rumback.

[9] In April 2023, MacKay's scored music for artist Michael Rakowitz' film I'm good at love, I'm good at hate, it's in between I freeze[10] MacKay has also been involved musically in theatre, appearing as musical guest in Chicago experimental theater troupe Neo-Futurists show Elements of Style in June 2023,[11] and in Little Carl, a production by Theatre Y in April 2023.

[12] "Among MacKay’s early inspirations were Miles Davis and Jimi Hendrix, but he also names British folk guitarist Davey Graham and Indian sarodist Ali Akbar Khan as influences.