For decades Them’s Van Morrison-era catalog wallowed in out-of-print purgatory due to contractual issues now largely lost to rock history. Back in the 1980 and ’90s, those of us wanting to explore the Irish group’s mid-’60s recordings for Decca had to resort to tracking down dusty vinyl copies of The Angry Young Them, Them Again and their string of singles. There simply didn’t exist many legitimately produced anthologies during the cassette and compact disc eras. It’s a situation that stretched deep into the current age of digital streaming, but fortunately, it has come to a close with the long-overdue release of The Complete Them: 1964-1967.

There’s no overestimating the historical value of this Legacy Recordings anthology, which is the first and last word on the brilliant music Them unleashed over the course of just a few years. Though they didn’t attain the dizzying commercial heights of The Rolling Stones, their scruffy and aggressive take on R&B-flavored beat music was as influential to the evolution of garage rock, hard rock and, later, punk. The few hits they did have — “Gloria,” “Here Comes the Night” and “Mystic Eyes” — became standards every up-and-coming band had to master. The Doors, Patti Smith and The Velvet Underground are a few artists deeply indebted to their feral stomp ’n’ howl.

But Them were far more than primal; they were progressive, too. Toward the end of 1965, they began exploring folk-rock and soul-infused singer/songwriter fare with dazzling results. “It’s All Over Now, Baby Blue” just may be the most sublime Bob Dylan cover ever attempted. Just as impressive are deep cuts “Hey Girl” and “My Lonely Sad Eyes,” which find the young and intensely sensitive Morrison inching closer to the ambitious sound he would realize on the 1968 masterpiece Astral Weeks.

In terms of fidelity, The Complete Them: 1964-1967 sounds fantastic. Numerous tracks are offered in mono and stereo. Of particular interest to completists will be the “true stereo” version of “Friday’s Child.” Recorded not long before Morrison’s departure in 1966, and released on an EP exclusively for the Dutch market, the gorgeous, acoustic ballad has seldom been heard by American ears, and to hear it the way it was intended is a genuine thrill. Whether you’re new to the Them legacy or an old school Van Morrison fan intimately familiar with his work, this anthology is essential listening.