He was a recording artist, but was best known as a pedagogue in the field of early plucked instruments in America, and an expert in musicians' hand anatomy.

He was active as a continuo lutenist, guitarist, citternist and theorbist, and performed throughout Europe and North America with the Harp Consort, Baltimore Consort, Schola Antiqua, New York City Opera; and at the Caramoor, Spoleto and Boston Early Music festivals.

He served on the faculties of the Mannes College of Music, the State and City Universities of New York and the annual Lute Society of America's Seminar.

[3] His students included, among others, Jozef van Wissem, Andrew Rutherford, Mara Galassi,[4] and Roman Turovsky[5] who in 2014 composed a tombeau on O'Brien's death.

[6] Patrick O'Brien has made several recordings with the Harp Consort, The King's Noyse and Paul O'Dette.