Drawn to music at an early age, Sonni first learned piano, then trumpet, switching to guitar at 14. His love of the instrument led him to leave the University of Connecticut where he was studying literature to attend the Hartford Conservatory of Music. After graduating, Jack was introduced to New York session guitarist Elliott Randall (famous for his solo on the hit "Reelin" In the Years") by keyboardist Michael Holmes, a graduate of Eastman & bandmate of Tony Levin & Steve Gadd.
Randall became a mentor & teacher and convinced Sonni to move to New York City and begin his career.
Jack lived in New York City from 1976 thru 1985 initially trying to break into session work but began focusing on his own band. In the late 1970s, Sonni"s band The Leisure Class had become a Monday night fixture at Kenny"s Castaways on Bleecker Street in Greenwich Village, the place for up and coming acts.
He visited the Knopflers in London, and after David (and then Hal Lindes) left the band, Sonni was asked to join the band for the 1984 recording sessions for Brothers in Arms and the subsequent tour. Jack accepted, and played guitar synthesizer on "The Manitoba"s Too Strong."
He began a second career as a marketing executive, first at Seymour Duncan, then Rivera Guitar Amplifiers followed by several years as director of marketing communications at Lincolnshire 6, a manufacturer of digital technology products for musicians.
In 2001 he moved on to become vice president of marketing communication for Guitar Center, primarily overseeing the company"s advertising, promotions and public relations, a position he left in 2006.
In the summer of 2006, Sonni left Guitar Center to return to a creative life as his first love, writing and begin work on a memoir project He moved to San Jose del Cabo in 2007, spending his mornings surfing and afternoons writing. After nine months in Baja, he moved to northern California, living in Healdsburg, California until January of 2012 when he relocated to Brooklyn for a short time.
Sonni spends his time now traveling, writing and working on several new web-based projects.