In its 27th year of cultural convergence, South by Southwest, arguably the country’s coolest sonic cotillion for musicians on the verge, will spotlight more Louisiana artists than ever before—and that’s just on the official event marquee.

Running March 12-17, the music component of the multimedia juggernaut, which also includes film and interactive technology, features more than 1,200 acts on the main bill—to say nothing of the offshoot showcases and partie...