Leyden moved to Portland, Oregon, in 1968 to take over the Portland Youth Philharmonic (then the Portland Junior Symphony) while long-time conductor Jacob Avshalomov went on sabbatical. He also joined the music department at Portland State University. He began his longstanding relationship with the Oregon Symphony in 1970 as associate conductor. This lasted for 29 seasons plus 34 seasons as conductor of the Oregon Symphony Pops. Over one million people attended his Oregon Symphony Pops concerts. In May 2004, he retired and was honored with the lifetime title laureate associate conductor. Leyden also served as the music director of the Seattle Symphony Pops for eighteen seasons, and as conductor of the Indianapolis Symphony Orchestra's Prairie Pops for eight seasons. He also conducted the Chappaqua Orchestra as its second music director before moving to the West Coast. He worked with Portland-based band Pink Martini and can be heard performing a clarinet solo on the title track of the band's second album, "Hang On Little Tomato".