I found the John Langan story "Outside the House, Watching for the Crows" in Paula Guran's anthology The Mammoth Book of Cthulhu (2016). It is by far the most professional story in the book, a tale behind which we sense with gratitude a real organizing aesthetic intelligence.
In it the narrator writes a letter to his son about his only supernatural experience. The narrator circles the subject, going back to adolescence.
Once upon a time, a kid named Jude handed him an audio cassette of music by a band called The Subterraneans. It's the kind of music that seems at first ephemeral; only later does he realize the album has snaked completely through his consciousness.
At which point he again meets Jude:
"Then you're fine," he said. "Holy shit. You know you're the first person I've met who actually saw something? Amazing."
"I don't understand," I said. "I'm sorry. I mean, I get that something important has happened – to me – but I don't know what it is."
"It's the music. It thins what's around you, lets you see beyond it."
I had read and watched enough science fiction to think I understood what Jude was talking about. "You mean to another dimension?"
"Sure," he said. "Dimension, plane, iteration, it's all just a way of saying someplace else. Someplace more essential than all of this." He waved his hand to take in the cars, the parking lot, the college, us.
"How— who are these guys? The Subterraneans? How did they do this?"
"I don't know. There are rumors, but they're pretty ridiculous. A lot of bands have messed around with occult material, usually as an occasion for some depraved sex. Fucking Jimmy Page and his sex magic. This is different. These guys are into some crazy mathematics, stuff that goes all the way back to Pythagoras and his followers. What they tried wasn't a complete success. Most of the people I've handed the tape to played it once and ignored it. A few became obsessed with it. Like I said, though, you're the first to see anything."
"Have you?" I said. "You have, haven't you?"
"Twice. Both times, I saw a city. It was huge, spread out along the shore of an ocean for as far as I could see. The buildings looked Greek, or Roman. A lot of them were in ruins, which made the place seem old, ancient. But there were people walking its streets, so I knew it wasn't abandoned. The ocean was immense. Its water was black. Its waves were half as tall as some of the buildings."
"Where is it?" I said. "Do you know what it's called?"
"No." He shook his head. "I spoke to a folklorist over at SUNY Huguenot. He'd heard of the city. He said it was called the Black City – also the Spindle. He thought it was another version of Hell. He was the one who told me about the Watch, the guys in the bird masks. Said you did not want to attract their attention."
"He didn't spell it out. I'm guessing a fate worse than death."
"They're coming here, you know."
For a second, I thought Jude was referring to the Watch, then I understood he meant the band. "Here? Where?"
"They're playing a show at The Last Chance. Late June, I forget the exact date."
"Are you going to go?"
"Are you kidding? You have to come, too."
"Look at the effect a recording of their material had on you. Imagine what hearing it live could do."
"I don't know." To be honest, I was as worried by the prospect of what your grandparents would say as I was any further visions. Depending on their moods, they had a way of making a request to do something new sound as if it were a personal injury to them.
"You cannot be serious," Jude said. "You're standing on the verge of . . ." He threw up his hands.
"Does it matter?" he said. "Really? Does it? Even if this place is a district in Hell, isn't that more than you're ever going to find, here?"