He wrote both songs and concert pieces, with his catalog numbering over 1000 works, including two string quartets, three symphonies, many chamber music compositions, and two operas.
In 2004 he released an album of songs in the rock'n'roll style, called Merseybeat, which featured guests Doug Fieger of The Knack and Big Jay McNeely.
In 2006 he released Merseybeat Mono, which contained all the songs from his first two albums in monophonic sound, as well as Concerto for Violin with Orchestra, the acoustic Fulton Avenue, and the single "She's Good".
Sprague's later releases included Merry Merseybeat Christmas (December 2006) and Merry Christmas, Traditional Carols arranged as Traditional Rock Songs (November 2007), "Fulton Chateau" (November 2008), and "String Quartets No.
In 2012, Sprague recorded a cover of the Bad Company single "Can't Get Enough" for a fund-raising CD titled Super Hits Of The Seventies, produced exclusively for radio station WFMU.