As an artist, Hammer is best known for his Guitarchitecture recordings, though he is also widely regarded as a leading New York City based soundtrack composer, having scored approximately 300 documentary films.

As a guitarist Hammer was a central figure within the Lou Reed Band that hosted the June 1979 concerts at The Bottom Line in New York City that included Don Cherry.

Hammer was accorded pioneer status by Rolling Stone, alongside an eclectic and select group, including Robert Fripp and Allan Holdsworth, having been attributed with leading a new era of development in the global guitar community, influencing instrument capabilities, form and functions in music.

Later that same year he worked with Laurie Anderson, triggering synchronized samples, from her Mister Heartbreak multitrack recordings live, utilizing the Digital Guitar Interface.

In 1989 Hammer designed AVA studios in New York City, a multi media production facility, that focused on film and digital music scoring.

Between 1994 and 2004 he composed soundtracks for an extended series of non fiction documentaries; collaborating extensively with The New York Times, National Geographic, Discovery Communications, and A&E Network.