Montgomery Land opened up a couple of years ago just a short walk from Ikebukuro Station. It's a standard issue narrow, basement bar with an incredible sound system. Master Iwasaki Yoshitsugu and his wife Kimiko-san run the place and are warm, chatty hosts. Within minutes of sitting down we were immersed in conversation about music and the Tokyo scene.
Iwasaki-san has a good collection covering all genres, with a lot of hard-bop records (and of course, a lot of Wes Montgomery albums.) Although it's a small place they host semi-regular live events at very reasonable prices, usually 2000-2500 yen. Ikebukuro has a surprising number of nice jazz joints and Montgomery Land is another great addition to the list.
Exit: East Exit
Distance from station: 6-9
From Ikebukuro Station East Exit take Meiji Dori all the way to the highway overpass, about six or seven minutes walk. Look left for the bright white sign.