Last September the Hideout held its 15th annual block party, and the same month the Onion‘s A.V. Club hosted its very first music festival. This year they’re combining forces and taking to the parking lot outside the Hideout for one gigantic celebration that features two days of music from Chicago and abroad. Music starts at 5:30 PM on Fri 9/14 and at noon on Sat 9/15, and tickets sold out weeks ago. On Friday indie-folk singer-songwriter Sam Beam, aka Iron & Wine, headlines; the evening’s other sets are from Irish singer Glen Hansard, shoegazy indie-rock act the War on Drugs, and local Krautrock revivalists Cave. Hometown heroes Wilco headline Saturday, after soul veteran Lee Fields & the Expressions, indie-rock duo Wye Oak, funky brother-sister act Wild Belle, Sleater-Kinney offshoot the Corin Tucker Band (see Soundboard), knockout singer Kelly Hogan, and others. Friday’s festivities begin with the Vision Celestial Guitarkestra, a massive, mystical assembly of droning guitars conducted by Steve Krakow, aka Plastic Crimewave; if you’ve got a guitar and an amp, you can join in, provided you get there before 5 PM. A portion of ticket proceeds goes to local schools and charities, including Rock for Kids, Literacy Works, and Drummond Elementary School. For more info, see Fairs & Festivals listings by day or visit hideoutchicago.com.