Chris Hillman became a country star as leader of The Desert Rose Band in the 1980s. Before that he had a reputation as being the ultimate sidekick.

First to Roger McGuinn and David Crosby in The Byrds, then to Gram Parsons in the seminal country-rock band The Flying Burrito Brothers and to Stephen Stills in Manassas. Now he has his own sidekick. Or rather Hillman and Herb Pedersen are sidekicks for each other.

They’ve been playing together since Desert Rose and are on tour as a duo with Hillman mostly on mandolin and Pedersen acoustic guitar. At their stop Thursday at the Iron Horse Music Hall in Northampton, Mass., they displayed consumate muscianship as they ran through a set of each other’s songs, Byrds tunes and classic country numbers.

What really sets this pair apart, though, is their beautiful vocal blend. Their voices mesh so well it’s like hearing one voice in perfect harmony. Pedersen has long been known as an excellent harmony singer, going back to Emmylou Harris’ breakthrough country hit in 1974 If I Could Ever Win Your Love, which Hillman and Pedersen performed second in their set.

Hillman and Pedersen have a wonderful rapport on stage and play it fast and loose, as Hillman said early in the set, they have a list of songs but don’t follow a setlist and play what they want to play.

They included other country standards such as a tribute to the late Vern Gosdin on Goin’ Up from Hillman’s first album with the Gosdin Brothers, The Hillmen, pre-Bryds in 1963. A two-song tribute to Buck Owens featured The Streets Of Bakersfield and Together Again. Others included the Danny O’Keefe classic Good Time Charlie’s Got The Blues, The Cowboy Way and the Burritos’ Sin City.

The biggest reactions were reserved for The Byrds songs, which Hillman and Pedersen executed so well in a bluegrass style, the listener didn’t miss some of the elaborate arrangements from the originals.

Turn, Turn, Turn, early in the set, not only featured their extraordinary vocal mix but also showed off Hillman’s considerable mandolin chops as he handled the 12-string guitar part and played a stunning solo. Hillman has been playing mandolin longer than he ever played bass, which he became known for in The Byrds, and he’s one of the country masters of the instrument.

The duo also played one of Hillman’s first country-rock compositions from the 1966 Byrds LP Younger Than Yesterday in Have You Seen Her Face, a pop-oriented song again showing off tight vocal harmonies. Eight Miles High, which Hillman recorded for his last album The Other Side, was a wonder with another crisp and proficient mandolin solo applied to one of the ’60s great pysche-rock songs. They also included Mr. Tamborine Man near the end of the set with the correct order of verses intact, unlike the single by The Byrds.

Pedersen had a few lead vocal turns as well, including his own Wait A Minute, a song about the difficulties of the musician always having to leave his family for the road. With such a reputation as the ideal harmony singer, one forgets what an interesting and pleasing lead voice Pedersen possesses.

They closed the main portion of their show with one of Hillman’s best compositions, written with Stills and Steve Hill, It Doesn’t Matter, from The Manassas album. After coming back for an encore, both met with the audience, something that has become common now at small venues for touring musicians.

They continue their tour through the fall with more stops in New England, both in Maine, before heading west. Hillman said they plan on recording a live album this fall with a full band. When an audience member shouted out near the end of the show why not record it here at the Iron Horse, Hillman, after thinking it over a second good-naturedly said “It could happen,” which drew a cheer and laughter from the crowd.