Alanis Morissette , Jack Johnson , Ty Dolla $ign , Vic Mensa , and St. Vincent are among the biggest musical names in a new round of programming SXSW announced on Tuesday for its 40th-anniversary edition, which kicks off March 12. Morissette will headline Spotify 20: Live at Stubb’s on March 14, a showcase marking Spotify’s 20th anniversary, where she’ll be joined by country artist Ella Langley, and a DJ set from St. Vincent. Johnson will perform a special set March 13 with Hermanos Gutiérrez —