This spot on the west side of Shinjuku Station is probably less conspicuous and therefore less likely to draw complaints (to the police, who then ask people to stop playing), but it also doesn't seem to generate many listeners. The plaza was good for getting an audience, but considering how often the police came around, chasing bands away from it in the autumn of 2008, probably it also generated complaints.
These guys seemed to sound pretty good, although I didn't stay very long. Anyway, here's what I heard:
新宿駅西口あたり ビレッジのライブ 東京
Their website is: http://ip.tosp.co.jp/i.asp?i=village0918
And - here's a still picture I took:
Lyle (Hiroshi) Saxon