The idea that the poetry of Ireland’s William Butler Yeats could be set to rock music and captured adequately (let alone eloquently) by Mike Scott and his Waterboys sounds pretentious at the least. Yet, they proved it possible with “Stolen Child” on Fisherman’s Blues, then with “Love and Death” off Dream Harder. Yeats and Scott share not only iconic status among their followers, they are also regarded as iconoclasts. The former was born a Catholic, became an atheist, and eventually found spirituality in nature and the occult. He was a celebrated poet and playwright but became a hard-willed, even ruthless politician in his defense of Irish freedom and unity. The latter is a controversial rocker and producer who has aspired to be a mystic, a social and political raconteur, a poet, and a traditional and postmodern balladeer. Also like Yeats, Scott’s art has been adventurous: he’s taken chances that have not always netted him critical — or commercial — success. An Appointment with Mr. Yeats contains 14 tunes adapted from the Irish poet’s works that are wedded to musical compositions by Scott (with fiddler Steve Wickham and Catalonian trombonist Blaise Margail helping on the charts). These last two are members of a ten piece Waterboys that include its members keyboardist James Hallawell, multi-instrumentalistKate St. John, bassist/co-producer Marc Arciero, flutist Sarah Allen and vocalist Katie Kim (who steals the show on the simple and sparse “Sweet Dancer,” one of the set’s finest moments.) The opener, “The Hosting of the Shee,” begins with Celtic reggae but becomes a Celtic rocker with swooping strings and layered guitars. On “News for the Delphic Oracle,” cabaret music gets transformed into Celtic cinematic stomp. There are hints of Scott’s last proper album, The Book of Lightning, evidenced by “September 1913” with soulful jazz piano by Hallawell, and “Politics” with its horn charts that could have been lifted from Dexys Midnight Runners’ debut album, Searching for the Young Soul Rebels. The all-too-brief “An Irish Airman Foresees His Death,” with its organs and Rhodes piano, get underscored by a military snare drum and Scott’s voice haunting in the verses. The only misstep is that “Let the Earth Bear Witness,” with its hymnodic reverence, should have closed the set instead of the ethereal “Faery’s Last Dance,” but that’s a minor quibble. Scott and his band have pulled off a gloriously wide-ranging celebration in An Appointment with Mr. Yeats; it is the Waterboys’ strongest effort since Room to Roam.