This section details a handful of releases that don't quite fall into any other category. Listed first are various albums by other artists on which SY as a whole make a guest appearance. Following this is a sampling of various pertinent side projects, typically involving more than one member (this is not a complete list of such items, however). For all other side project info, I refer you to a few higher sources below. I stuck the "Sensational Fix" book here too, since it does contain a musical contribution from each member.
The second is Sonic Youth's own discography, given away at the June 13th, 1999 show in NYC:
For a great Jim O'Rourke discography, go here.
If there's no frame at the top of this page, click here.
artist
title
year
primary label
SONIC YOUTH GUEST APPEARANCES
MIKE KELLEY
Plato's Cave, Rothko's Chapel, Lincoln's Profile
1987
High Performance Records
MOE TUCKER
Life In Exile After Abdication
1989
50 Skidillion Watts
WILLIAM S. BURROUGHS
Dead City Radio
1990
Island
CAN
Sacrilege
1997
Mute
ROSWELL RUDD
Broad Strokes
2000
Knitting Factory
BRIGITTE FONTAINE
Kekeland
2001
Virgin
MATS GUSTAFSSON + SONIC YOUTH
Hidros 3 (to Patti Smith)
2004
Smalltown Supersound
SONIC YOUTH
Sensational Fix
2008
LiFE and Museion
HEAVILY BAND-RELATED SOLO/SIDE PROJECTS
VARIOUS ARTISTS
Just Another Asshole
1981
Atavistic
VARIOUS ARTISTS
Guitarrorists
1991
No. 6
LUCKY SPERMS
Walking the Cow/Tomorrow Never Knows
1991
Ecstatic Peace!
MIRROR/DASH
Electric Pen/Gum
1992
Ecstatic Peace!
VARIOUS ARTISTS
Outlaw Blues
1992
Imaginary
VARIOUS ARTISTS
Fortune Cookie Prize
1992
Simple Machines
THURSTON MOORE
Psychic Hearts
1995
DGC
THURSTON MOORE
Cindy (ROTTEN TANX)
1995
DGC
THURSTON MOORE
Ono Soul
1995
DGC
MALE SLUT
The Church Should Be For The Outcast, Not A Church That Casts People Out
1995
Stomach Ache
MIKE WATT
Ball Hog Or Tug Boat?
1995
Columbia
LEE RANALDO
Amarillo Ramp
1998
Starlight Furniture Co.
CHRISTIAN MARCLAY/THURSTON MOORE/LEE RANALDO
Fuck Shit Up
2000
Victo
KIM GORDON/IKUE MORI/DJ OLIVE
SYR 5
2000
SYR
THURSTON MOORE, LEE RANALDO, STEVE SHELLEY with MATS GUSTAFSSON
Without Kim
2000
Olof Bright
VARIOUS ARTISTS
Black Box
2000
Olof Bright?
THURSTON MOORE/LEE RANALDO/STEVE SHELLEY/JIM O'ROURKE
Melbourne Direct
2006
Saucerlike Recordings
THURSTON MOORE
Trees Outside the Academy
2007
Ecstatic Peace!
I opted not to travel too far down the side project road for purposes of this site, however I can provide you with a few fairly detailed documents that do cover this territory. The first is Henry Weld's original side project / pre-SY discography, which you can view here.
For more solo project information, I recommend checking out Wolfgang's discography here.