Jam sessions are the sweaty workout of the jazz world, where musicians go to pump up and get in shape. It's a classroom, too, where aspiring players can get their lessons and take their lumps. While most professional musicians graduate from these sessions, most nights, after the clubs close, the pros still gather to jam.

Tokyo has many, many jam sessions, many of them unadvertised and hard to find. As it has always been, the inner world of jazz can be slightly secretive, and even more so in a city like Tokyo, where it is hard to find places even when you do know where you are going. Rest assured, though, all kinds of late night spaces open up their space to opening up the music. The jazz world needs these like the earth needs its forests—they generate a lot of musical oxygen.

Below are a few of the best known jam sessions, but anyone reading this who knows of others should send me an email and I'll add it to the list. Be forewarned that some jam sessions do charge an entry fee and others are organized by level. Times change, though, so anyone with instrument in hand should check the websites closely for the latest listings. I've listed them by days of the week, but holidays and special sessions often take priority. Sessions start around 7 or 8 unless otherwise noted.

Sunday
Shibuya, KoKo, www3.point.ne.jp/~ko-ko/
Miles Café, Ikebukuro, www.milescafe.com/jam.html
Half Tone, Tachikawa, www007.upp.so-net.ne.jp/halftone/
Jam House, Meguro, www.geocities.jp/megrojamhouse/info.html

Monday
Cotton Club, Takadanobaba, www.intro.co.jp/cotton/index.php
Miles Café, Ikebukuro, www.milescafe.com/jam.html
Rooster North Side Ogikubo, www.ogikubo-rooster.com Blues!
Jam House, Meguro, www.geocities.jp/megrojamhouse/info.html

Tuesday
Miles Café, Ikebukuro, www.milescafe.com/jam.html
Half Tone, Tachikawa, www007.upp.so-net.ne.jp/halftone/
Jam House, Meguro, www.geocities.jp/megrojamhouse/info.html
Django, Sendagi, www.jazzclubdjango.com

Wednesday
KoKo, Shibuya, www3.point.ne.jp/~ko-ko/
Rooster North Side Ogikubo, www.ogikubo-rooster.com
Jam House, Meguro, www.geocities.jp/megrojamhouse/info.html

Thursday
Cotton Club, Takadanobaba, www.intro.co.jp/cotton/index.php
Half Tone, Tachikawa, www007.upp.so-net.ne.jp/halftone/
Manhattan, Asagaya, www.ateliermw.com/manhattan

Friday
Miles Café, Ikebukuro, www.milescafe.com/jam.html
Manhattan, Asagaya, www.ateliermw.com/manhattan (from 01:00 a.m.)
Jam House, Meguro, www.geocities.jp/megrojamhouse/info.html

Saturday
Intro, Takadanobaba, www.intro.co.jp. All night jam session.
Cotton Club, Takadanobaba, www.intro.co.jp/cotton/index.php
Miles Café, Ikebukuro, www.milescafe.com/jam.html
Manhattan, Asagaya, www.ateliermw.com/manhattan (from 01:00 a.m.)
Jam House, Meguro, www.geocities.jp/megrojamhouse/info.html