You'll never know what will happen in the world of music when SXSW is going on. From surprise appearances at concerts, to actual mixtapes being released during the weak, the annual festival in Texas keeps people on their feet until the final day. Last night, Wiz surprised his SXSW audience by dropping a new track titled "Rain" featuring OVO singer PARTYNEXTDOOR. The video (caught by The Trophy Life) is very brief, but from what we hear, PARTYNEXTDOOR supplies the smooth hook, while Wiz supplies the raps. Check out the clip below.