It was during his years as a graduate student that he first began to be interested in old-time music, particularly the traditions of the North Carolina Piedmont area and Appalachia, and it was no wonder as there was a great deal of interest in these styles among students and other music fans in this area. Fellow graduate student Tommy Thompson hosted weekly and often more frequent jam sessions and house party concerts, and out of these musical soirées several different ensembles evolved. Jabbour was a member of the Hollow Rock String Band, a quartet which also featured Thompson and fiddler Bill Hicks, both of whom would go on to become members of the Red Clay Ramblers. Jabbour began studying under the old-time master Henry Reed, felt that he was the number one influence on he and his group musically, and was sad that the debut album by the Hollow Rock band was not released until a few months after Reed's death in 1968.

Although Jabbour has recorded off and on, including the Flying Fish album Sandy's Fancy, and has performed at a variety of folk festivals and other events, his main activities have been as an academic: folk culture researcher and archivist. In 1968, he took an appointment as a professor of English and related folklore at the University of California in Los Angeles. The next year he jumped to the Archive of Folk Song, later to become the Archive of Folk Culture at the Library of Congress. An accomplishment there that is treasured by old-time fiddle fans is the anthology Jabbour put together from the archives, released in 1971 under the title American Folk Tunes. He then took on a long and ambitious three-year project in collaboration with researcher Carl Fleischauer based on studying the folk traditions of a single Appalachian family. Out of this epic activity came the Library of Congress two-record set The Hammons: A Study of a West Virginia Family. In 1974, Jabbour received an important position at the National Endowment for the Arts, starting up that agency's grant program for folk artists. This program became a very important source of revenue for a variety of projects related to folk traditions, including new recordings, teaching, and study possibilities for young and old players alike and package tours involving many classic American artists. He was the founding director of the American Folklife Center at the Libary of Congress in 1976 and stayed in this position for 23 years before his retirement in 1999.

To commemorate his retirement and to continue giving back to the musical traditions that inspired him through much of his adult life, he established the Henry Reed Fund for Folk Artists. In the '90s he was also active as a producer of folk music recordings, including collaborating with Grateful Dead drummer Mickey Hart on the well-received Rykodisc series of international recordings. The subject material ranges far from the Appalachian hollows Jabbour is most associated with, including recordings from Latin America, Indonesia, and Africa. He also assembled an anthology of fiddle music for Rounder in the late '90s.