Near the end of Sufjan Stevens’ solid, if somewhat uneven, set at Castaways Wednesday night, one especially zealous fan in the front yelled for Stevens to play “Decatur,” a song off of his excellent 2005 album, Come on Feel the Illinoise. The request rose easily above the crowd’s quiet murmuring, but before Stevens could respond, another fan demurred for him.

“Play whatever you want!” the fan yelled, prompting a whooping response from the majority of the crowd.

By that point in the show, the request seemed more a statement of fact than a gesture of deference. Stevens’ performance at Castaways, the third night of a 16-stop intimate fall tour, often seemed an exercise in self-determination. The first five songs of the singer’s 13-song set were all new and unreleased material.

“This is going to be like live workshop,” Stevens conceded after introducing another new song.

Most performers can’t get away with this kind of self-indulgence when choosing their set lists. Then again, most performers can’t get away with a lot of what Sufjan Stevens gets away with.

On his boldest songs, Stevens employs classical motifs — lush orchestration, intricate arrangements, contrapuntal melodies — though in an unmistakably rock-and-roll-centric framework. The result sounds something like the progeny of Bach and Bowie, the work of a juiced-up, laboratory-conceived, whiz-kid composer. Which is why Stevens’ music is so conspicuous: Stuff this huge should fail.Singing in the Dark: Sufjan Stevens was quiet and reflective on Wednesday night, playing many of his new, more experimental numbers.

It hasn’t — so far. Judging by Wednesday night’s set, though, Stevens’ sonic exploration is lurching in a decidedly different, even more ambitious direction.

These new songs find the indie maestro dabbling in jazzy, jammy electronica, deploying drum kits and demented horns and blip-and-bleep effects, occasionally to dazzling results.

The first encore, “There’s Too Much Love,” was one stunning example. Spacey effects and a punchy breakbeat — sounds so unexpected they elicited shocked laughter from several in the audience — sustained the song’s verses, before giving way to a poppy, ebullient chorus that had Stevens offering what sounded like an apology but felt closer to a celebration: “There’s too much riding on that / There’s too much, too much, too much love.”

However, the new songs were only fitfully enthralling, too often veering into prolonged passages of free-form improvisation — more like Soulive than Sufjan.

In terms of shock value, this shift in styles isn’t quite Lil Wayne doing hard rock. But it’s surprising nonetheless, especially for fans expecting more of the hushed and wistful acoustic numbers that count for much of Stevens’ most beautiful material. In fact, Stevens himself seemed aware of the burden the new songs were placing on listeners.

“Enough of this glam-rock bullshit,” he joked, before launching into “The Transfiguration,” a selection from Seven Swans, his spiritually-themed 2004 album.

This line may have been in jest, but Stevens did fill the remainder of his set (excluding the first encore) with material from Illinoise and Seven Swans.

In contrast to the flashy musicianship of his new material, Stevens’ older, stripped-down songs sounded especially poignant Wednesday night. These songs burned with a raw pathos that Stevens’ new ones seemed too varnished to spark.

On “Casimir Pulaski Day,” a song from Illinoise about a friend dying of cancer, Stevens harmonized in quavering falsetto with female singer Nedelle Torrisi (of the opening band, Crypoticize), moving the crowd to silence.Let's do it together: Nedelle Torrisi of Cryptocize opened the show joined Stevens on a duet.

Stevens tweaked “Chicago,” probably his most popular and anthemic song, by fusing its several adaptations into a hybrid version that took most fans the first verse to recognize. Still, this novel version was as stirring as the original.

The night’s most haunting moment, however, was its last one. Performing a second encore, Stevens again silenced the crowd with a hushed acoustic number — this time, Illinoise’s “John Wayne Gacy, Jr.,” a song about a serial killer who raped, tortured and murdered teenage boys, and buried them under the floorboards of his house. What makes the song so chilling is Stevens’ effort to empathize with Gacy, as most blatantly obvious in its last two lines.

“In my best behavior, I’m really just like him,” Stevens sings. “Look beneath the floorboards for the secrets I have hid.”

Upon finishing Wednesday night, Stevens took off his guitar and abruptly walked offstage. The crowd at Castaways cheered, lingering, looking dazed under the house lights. Many hung around, discussing with friends the new material. A few, though, were beginning to eye the door.