J Mascis is best known as a founding member and guitarist of Dinosaur Jr., a band formed in 1984 that recently experienced a resurgence after reforming in 2005. After Dinosaur Jr. originally disbanded, J Mascis started another band entitled J Mascis + The Fog. Most recently J Mascis released a solo album entitled Several Shades of Why in March of this year. J Mascis is a truly talented guitar player, who even has a Fender guitar names after him.
Check out J Mascis with a solo performance of "Ammaring" off the J Mascis + The Fog 2000 record More Light. The guitar alone is worth the listen.
You can find more J Mascis info on his website, such as his scheduled tour date in DC in September!