This Peter Green-led edition of the Mac isn't just an important transition between their initial blues-based incarnation and the mega-pop band they became, it's also their most vital, exciting version. The addition of Danny Kirwan as second guitarist and songwriter foreshadows not only the soft-rock terrain of "Bare Trees" and "Kiln House" with Christine Perfect-McVie, but also predicts Rumours. That only pertains to roughly half of the also excellent material here, though; the rest is quintessential Green. The immortal "Oh Well," with its hard-edged, thickly layered guitars and chamber-like sections, is perhaps the band's most enduring progressive composition. "Rattlesnake Shake" is another familiar number, a down-and-dirty, even-paced funk, with clean, wall-of-sound guitars. Choogling drums and Green's fiery improvisations power "Searching for Madge," perhaps Mac's most inspired work save "Green Manalishi," and leads into an unlikely symphonic interlude and the similar, lighter boogie "Fighting for Madge." A hot Afro-Cuban rhythm with beautiful guitars from Kirwan and Green on "Coming Your Way" not only defines the Mac's sound, but the rock aesthetic of the day. Of the songs with Kirwan's stamp on them, "Closing My Eyes" is a mysterious waltz love song; haunting guitars approach surf music on the instrumental "My Dream"; while "Although the Sun Is Shining" is the ultimate pre-Rumours number someone should revisit. Blues roots still crop up on the spatial, loose, Hendrix-tinged "Underway," the folky blues tale of a lesbian affair on "Like Crying," and the final outcry of the ever-poignant "Show Biz Blues," with Green moaning "do you really give a damn for me?" Then Play On is a reminder of how pervasive and powerful Green's influence was on Mac's originality and individual stance beyond his involvement. Still highly recommended and a must-buy after all these years, it remains their magnum opus. ~ Michael G. Nastos, All Music Guide