After a seven-year association with Trinity Cathedral in downtown Pittsburgh, he is now priest-in-charge for the Church of the Incarnation, a new congregation with an emphasis on creativity and the arts. Before ordination he worked for eighteen years as an announcer/producer and Manager of Community Broadcasts for WQED-FM, Pittsburgh.

While Johnston pursued and completed an undergraduate degree in music education at Andrews University (B.Mus.1980) with tuba as his performance area, his most meaningful experience was being able to work at WAUS-FM, AU's radio station. Following three years of teaching at AU’s laboratory school, he took an on-air position with KWHO/KWHO-FM in Salt Lake City. He subsequently worked for Brigham Young University's broadcast services, serving as broadcast host for the Utah Symphony Orchestra. He also wrote music criticism.

In 1986 he accepted an invitation to join WQED-FM, a classical music station, where he worked until 2004. During those years, the Pennsylvania Association of Broadcasters twice named his program as Best Public Affairs Program/Series. He was awarded the Golden Quill by Pittsburgh journalists for his overseas arts reporting.

He has also been a contributor to such radio networks as National Public Radio (NPR), American Public Media, NHK Japan, Vatican Radio, and Minnesota Public Radio. Behind the controls, he recorded for NPR's Performance Today, Pipe Dreams, All Things Considered, and other programs. Johnston once described his 25-year career in radio as the fulfillment of a "magnificent obsession" that had started when he was in the eighth grade.

Johnston is also Artist-Lecturer in Music History at the Carnegie Mellon University School of Music, a position he has held since August 2005. He created the first online course to be offered in the School of Music, "Repertoire & Listening for Musicians," a four-semester repertoire literacy and critical listening proficiency class required of all music majors. Other courses include Survey of Western Music History, Music History II (Classical and Romantic), Music of the Spirit, and Survey of Historical Recording.

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