Influential music mag Rockin' On already holds massive Japanese festivals every summer (Rock in Japan) and winter (Countdown Japan), but that didn't stop it from launching a new event last spring. Japan Jam is a little different: rather than play a run-through of their greatest hits, the performers do one-off sessions with guest musicians, and pretty much anything is fair game. This year's bill includes popular guitar bands The Back Horn, Sambomaster, 10-Feet and Zazen Boys – the latter playing with (or against?) free jazz musicians and psychedelic troubadours. The inaugural Jam, held at Fuji Speedway, was marred somewhat by lousy weather, so they've wisely moved things to the indoor Makuhari Messe complex this time around.