If “the girl with kaleidoscope eyes” were a musician, she might well have composed something like Terry Riley’s 2014 concerto for organ and orchestra, At The Royal Majestic, a tie-dyed psychedelia of genres and allusions replete with its own newspaper taxis and cellophane flowers. Infused with a reverence for the mighty movie palace organs of the 20s and 30s, it closed the first half of the Boston Symphony’s second program of 2017.

Riley is often called “The Father of Minimalism” but his recent works have expanded well beyond any textbook definition of the term. “Maximal minimalism” might best describe his concerto, which flows in a riot of surreal free association through three movements and employs a large and varied orchestra. The first and longest movement, “Negro Hall”, mixes boogie woogie, jitterbug, gospel, jazz syncopation and the waltz with shifts in meter and tempo adversarially layered and juxtaposed à la Ives. “Lizard Tower Gang”, the second and briefest movement, seeks, in the composer’s own words, to “juggle chaos and symmetry” with ragtime morphing into blues and a parade-like cadence devolving into a funeral cortege. “Circling Kailash” transports us from ragtime to raga on a pilgrimage around the holy mountain in Tibet sacred to Shiva set to rolling waves of repeated melodic fragments dotted with the sound of temple bells and jarred by the intrusion of a circus calliope. Like any great Hollywood epic, At The Royal Majestic ends in a fade-out, the organ solo slowly exhaling a tone backed by a hum more felt than heard.

The dynamic and irrepressible Cameron Carpenter, who premiered the concerto, made merry across the key and pedal boards, his bedazzled Cuban heels adding visual flash to his brilliant virtuosity. Bramwell Tovey took a few minutes for a witty, self-deprecating introduction of the piece and the unusual forces marshalled to play it, carefully pointing out, for example, that the three piccolos were meant to play out of tune. He then unleashed the orchestra’s innate flower power in Peter Max bursts of color and Pop Art arabesques. Many who grew up in the 60s and 70s are still wondering, “What was all that about, anyway?” On a first hearing, At The Royal Majestic can leave you with a similar feeling… but, man, what a trip!

Composed in the 60s, Samuel Barber’s Toccata Festiva is definitely not of the 60s. A dedicatory piece commissioned to celebrate the installation of the first organ at the Academy of Music in Philadelphia, it showcases the instrument’s capabilities and the organist’s skills in a virtuosic, celebratory call and response between soloist and orchestra, written in Barber’s characteristic lyrical, romantic style. Carpenter dazzled in a cadenza written exclusively for the pedalboard, feet as fleet and fluent as Fred Astaire’s flying to the furthest reaches of the console leaving him knock-kneed. The joyous peal of organ, timpani and brass shook the house and set the floor vibrating in a bone-rattling climax.

Carpenter followed the Riley with two encores, then returned after intermission to play the organ part in the final work: Elgar’s 14 Variations on an Original Theme, Enigma. Tovey, conducting from memory, led a generous, polychromatic performance, not pausing until after the ninth variation, “Nimrod” and then only twice more, after the tenth and eleventh. Elgar’s good-natured teasing shown through whether poking fun at RBT’s amateur theatrical pretensions, Troyte’s losing battle with his piano or the otherwise spritely Dorabella’s stutter. Under Tovey’s direction, BGN became the shorter brother of the psalmodic “Nimrod” and “Edu” avoided self-congratulatory bombast ending the program with a celebration of Elgar's self-confidence.