Ask Alex Maas to define “psychedelic,” and he’s got an answer ready. “Eighteen grandmothers in a yellow polka-dot bikini, playing banjo onstage,” he says. It’s a shitty, sarcastic answer, sure. But you gotta figure that, as frontman for the Black Angels, founders of Austin Psych Fest and a band that named itself for a Velvet Underground song and worshipped the cosmic drone back in the early ’00s when rhythm-obsessed bands like Joy Division and Gang of Four were the retro tunes of choice and the phrase “Tame Impala” meant fuck-all to anyone, he’s probably heard that one before. Turns out this is just one more case where the dictionary is even less helpful than a rock star. “Psychedelic,” says Merriam-Webster, is a noun meaning “a psychedelic drug (such as LSD).” But let’s assume our friends are lame, and scoring Lucy in order to better understand an article just isn’t an option. We’re back to the grandmothers and the polka-dot bikini, which doesn’t much describe the band’s sound. If it’s any help, Maas names like-minded visual artist Alex Grey as a fellow psychonaut. For the uninitiated, the music of the Black Angels, free from its more complicated antecedents, might be the Platonic ideal for psychedelic music, combining that famous Velvet hum with the self-serious lyrical poetry of Jim Morrison (not hating — somebody has to bring in the wood for carving, as Ezra Pound says). To put it another way, the Black Angels are the only hipster-era band likely to write a war protest song with zero irony. But they aren’t interested in rehashing the Flower Power era, Maas says. It’s more complicated than that. “If a song sounds good, if it makes us feel good, then we’ll keep playing it,” Maas says. “It might be more hip-hop psychedelic, it might be more traditional ’60s psychedelia, it might be folk psychedelic music or surf or garage. There’s so many different genres, so it’s kind of difficult to just focus on one thing.” Their latest, Indigo Meadow, moves through all of these sub-genres and then some without missing a mind-blowing beat, while baiting hooks with catchy choruses and offering heavy-handed but timely criticism on “Don’t Play With Guns.” According to an article in LIFE published in 1969, “true ‘acid rock’ goes deeper than just lyrics. It employs a monotonous, harshly amplified drone sound which can act as a psychedelic stimulus,” and that seems fair. Without Owsley Stanley’s kitchen-sink acid, there’d be no USA, circa 1967, and without 50 years of drug-abusing rock stars, there’d be no Black Angels. Even if they can’t define it, the Black Angels are the standard-bearers for modern psych-rock, and if you ever do get ahold of those drugs, you’ll be goddamn glad they’re here.

Following a tour of the exhibition “Fiesta, Fête, Festival” (1pm), and a taste of fairground fare (1:30pm), the McNay screens Carlos Saura’s Flamenco (2pm), a 1995 documentary tracing the roots and rhythms of the art form.

Michael D. Burger directs Rob Barron’s Henchmen, the second installment of the Chronicles of Nerdology. Set in a warehouse, the play focuses on a captive superhero while an epic battle rages outside.

“Guns N’ Roses,” according to the press release for the inaugural day-long Bud Light River City Rockfest, “are Axl Rose, DJ Ashba … Ron ‘Bumblefoot’ Thal...” Not in my America, bucko. To be fair, I guess, Bumblefoot is every bit as much Slash as Rose circa 2013 is Rose circa 1987. But we didn’t come here to gloat over the decades-long decline of a former World’s Coolest Motherfucker titleholder, we came to watch Rose do live-band karaoke renditions of the hits, dammit. Local heavy hitters the Heroine, however, still have the Appetite for Destruction, and their live show is insane even when they aren’t playing big festivals with Hall of Famers. They will be the band to watch. Raised on GNR, not to mention fellow fest act Alice in Chains, the Heroine and fellow San Antonians Memory of a Melody have the energy and the motive to put on a show Axl might’ve a quarter century ago.

An innovative collaboration between the Office of Historic Preservation, the Department for Culture and Creative Development, and the Center City Development Office, the Center City Open House series is designed to showcase the potential of San Antonio’s vacant historic buildings.The inaugural event takes over a 1920s-era building at 201 West Commerce with a dynamic art display spanning the entire facade of the building (featuring artists Rex Hausmann, David Almaguer, and Kyle Martin), a performance of "Da Luz" by Ballet San Antonio, a "Barrio Couture" fashion presentation by local designer Agosto Cuellar, complimentary drinks courtesy of Freetail Brewery, and  international hors d’oeuvres by Ming’s Thing.

If you missed the recent Tejano Conjunto Festival, don’t despair — two of this year’s hottest acts will grace the Arneson River Theater stage in a “tribute to the kings of accordion.” It’s a fitting homage, as Juanito Castillo and Dwayne Verheyden are exemplary protégés of their respective masters. Castillo, a young San Antonio native, hooked up with legendary Steve “Esteban” Jordan and absorbed the late Jimi Hendrix of the accordion’s magical, genre-pushing style. Verheyden, a baby-faced 22-year-old from the Netherlands, looks to Flaco Jiménez for his precise conjunto mastery. Both will play backed by a band comprised of notable players like Gabriel Zavala, host of KSAT’s Tejano y Más program (and a member of Lush and Stefani Montiel’s band), and Jaime Villanueva, a longtime guitarist for Jordan. The Michael Guerra Band opens.