He was already an experienced keyboard player when he joined Captain Beefheart's Magic Band in 1976, in which he also played bass. Like other members of the band, Feldman was expected to capture (on tape or notepad) Beefheart's musical ideas. Once instrumental parts had been created, the band members had to play them exactly as composed: "I never had a problem with that. I felt like I was getting parts dictated to me from one of the best, especially when they were designed for me. You just feel like a model in a fashion show wearing a really nice dress, I guess." Feldman worked on the acclaimed trio of Beefheart albums in the late 1970s and early 1980s that turned out to be the last of the Captain's musical career, Shiny Beast (Bat Chain Puller) (1978), Doc at the Radar Station (1980), and Ice Cream for Crow (1982).
Feldman met the Pixies' Frank Black in 1991, when Pere Ubu were touring as the Pixies' opening act, and later played keyboards on the Pixies' Trompe le Monde (1991) and toured with them. He can also be seen in the video for Alec Eiffel. After the Pixies split, Feldman worked with Frank Black on his solo albums Frank Black (1993) and Teenager of the Year (1994).
In 1994, after two Frank Black albums, Feldman applied for a job with PJ Harvey, who was putting together a band. He played on To Bring You My Love (1995) and Is This Desire? (1998), and has regularly toured with her. His band kNIFE & fORK has opened for her.
While in Australia touring with Frank Black he met the Australian band Custard. He recorded two albums with them in the USA; Wisenheimer (1995) and We Have the Technology (1997).
In 1998, he produced Jesus Hits Like the Atom Bomb (1998) by Dallas group Tripping Daisy. He later produced Together We're Heavy (2004) by the Polyphonic Spree, a 24-member troupe containing three ex-members of Tripping Daisy. He also produced the album Revival (2000) by Brooklyn singer-songwriter (and sometime Frank Black songwriting collaborator) Reid Paley.
Through the 1990s Feldman continued to tour on and off with Frank Black and the Catholics and joined the band in the studio to make Dog in the Sand (2000), as well producing the unreleased album Sunday Sunny Mill Valley Groove Day.
On April 25, 2008, Eric performed live with Black Francis (and band) at the San Francisco film festival, in the Castro Theatre. Black Francis and band performed an original score for the 1920 silent movie "The Golem."