The platonic ideal of South By Southwest is stumbling upon a band you’ve never heard and finding a new favorite for life. The reality is that most bands are average, and there’s more noise than signal within the overwhelming selection of performers at Austin’s annual industry bacchanal. So whenever it actually happens — when you wander into a room and are gobsmacked, delighted, electrified — it’s to be celebrated, not to be taken for granted.

That’s how it went Wednesday afternoon during Brooklyn Vegan’s party at Mohawk. When Militarie Gun wrapped up on the outdoor stage, I wandered indoors to see who was playing and soon learned it was Sweet Pill, a five-person emo band from Philadelphia. Admittedly, Sweet Pill are not totally obscure. They’re signed to the perennially excellent Topshelf Records, and a quick search through my inbox revealed about a dozen press releases promoting last year’s Where The Heart Is. But a music blogger’s email account is kind of like the online version of Austin during SXSW all year round, and Sweet Pill got lost in the wash.

You can trust that I’ll be paying close attention for the next announcement because holy shit! Sweet Pill! They were so arresting at Mohawk that I had to see them again Thursday night at Topshelf’s official SXSW showcase at Cheer Up Charlie’s, where their performance on the outdoor stage around midnight was even better. Where The Heart Is is a very strong record, but I feel blessed to have discovered Sweet Pill through their live show. These five are great musicians, great songwriters, great performers, and seemingly great friends too. Onstage, that all adds up to an immensely charming powerhouse.

Sweet Pill pull together a few different strains of emo. There’s the inevitable resemblance to early Paramore, what with singer Zayna Youssef belting out melodic rallying cries while the rest of the band roars and surges in anthemic fashion. There’s also quite a bit of the twinkly, mathy, post-American Football guitar virtuosity that popped off in the early 2010s emo-revival era, as well as an epic heaviness seemingly borrowed from post-hardcore. It all combines seamlessly into songs that obliterate the distinctions between power and finesse, between pop and hardcore, between emo and the larger continuum of crowd-pleasing rock ‘n’ roll.

Guitarists Jayce Williams and Sean McCall have a telepathic connection. Their instruments interlock majestically throughout a Sweet Pill show, sometimes trading off precise rapid-fire riffs, other times converging on the same hard, heavy power chord and beating it into submission. I’d say it reminds me of Nick Valensi and Albert Hammond Jr. except the sound here is far more “Warped Tour at its impeccable peak” than “performatively ragtag CBGB revival.” The interplay between the guitars is so captivating that you might miss how many dazzling drum fills Chris Kearney works in without losing the crisp, violent snap that drives Sweet Pill’s songs forward and dramatically halts them at just the right times. The three of them plus bassist Ryan Cullen are all extremely well-rehearsed; rather than get bogged down in such technical music, they make intricate compositions feel fluid and resoundingly alive.

But the star of a Sweet Pill show is undoubtedly Youssef, one of the most charismatic frontpeople I’ve seen in years. She bounds around the stage with wild-eyed enthusiasm: stomping and thrashing like Henry Rollins, communing with the crowd through her endlessly expressive face, relishing her bandmates’ prowess with finger-points and air-guitar outbursts. She is a bracingly physical presence, a true performer. Just as importantly, the woman can sing. Song after song, she sends her voice soaring without hitting a bum note. It’s remarkable. Occasionally, Youssef switches over into a grotesque roar that suggests she could just as easily front a far nastier band than this. But I’m glad she’s fronting Sweet Pill because Sweet Pill are incredible.