I've put together a list of all the guest appearances in the Dead's early shows. I don't know of a site that provides a listing like this, and it's likely that I've forgotten or left out some guests, so if anyone notices something missing, please speak up!
This list is mostly limited to electric Dead shows where someone outside the band added a musical contribution. It doesn't include the acoustic sets of 1969-70 (which often had many guests), since I'll be talking about those in another post (that will be a kind of "part II").
It doesn't include the New Riders - though I should at least mention the 3/18/73 New Riders show where Garcia, Weir, and Godchaux all join in.
It doesn't include announcers - some of whom, in the early days, are quite entertaining in their own right.
It doesn't include studio sessions (for instance, the Jon Hendricks session in March '67). For a good discography and listings of various studio collaborations, check www.deaddisc.com - and for Garcia's non-Dead projects, check www.thejerrysite.com (he played on SO many other bands' albums).
It doesn't include the collaborations with David Crosby in late '70 (for instance, the PERRO sessions or the 12/15/70 show), which could be a whole separate discussion.
It doesn't include the many tapes of Garcia jamming with other musicians - for instance, Country Joe (the Fillmore West '69 "Donovan's Reef jam"), Jefferson Airplane (Family Dog 9/6/69), the Allman Brothers (Cow Palace 12/31/73), or Doug Sahm (Austin 11/23/72), or various early jams with Jorma Kaukonen & Jack Casady.
But I did include a couple illuminating non-Dead shows that happen to be on the Archive, where Dead members have a strong presence, as well as the notorious Hartbeats shows since those have so much Dead material.
I've decided to skip the early '66 Acid Tests, since they're so full of audience mikes and Prankster chatter - the Dead themselves were the guests. So we'll start at the dawn of 1967:
12/1/66 Matrix - An unknown blues singer & harmonica player joins the Dead for Yonder's Wall and My Own Fault.
1/14/67 Great Human Be-In - During a speedy instrumental Schoolgirl, Charles Lloyd plays flute and does a jazzy, aggressive stream-of-consciousness rap.
6/18/67 Monterey Festival - This is the earliest version of Alligator we have - at the beginning of Alligator, someone's playing harmonica where the verses should be. It doesn't seem to be Pigpen, since it's off-key (meanwhile he's probably singing into a dead mike) and later in Caution he plays harmonica in his usual style - but I had the impression it might be someone familiar with the song.
7/23/67 Straight Theater - Garcia introduces Neal Cassady, who raps for a while while the Dead back him. For the first part they play an instrumental Lovelight (their first known version), then in the second part they get into a minimal 'space' - also the earliest space. Apologies for the link - it seems to be only two minutes (the original record was ten minutes, and even that was an excerpt).
6/19/68 Carousel Ballroom - After the Lovelight, the Dead stop the music for twenty minutes of audience chanting. For the second half of the show, the Dead are joined by an unknown guitarist, and perhaps Jack Casady.
9/20/68 Berkeley - In this snippet of a show, the Dead abort a short Eleven to go into drums - they're joined by two more drummers for a 25-minute drum solo, which ends the show with cries of "Ya, ya, yaketa!" Perhaps equipment or lysergic troubles prevented an Alligator jam - in any case, this must be the longest drum solo until 1978. http://www.archive.org/details/gd1968-09-20.sbd.miller.32900.sbeok.flac16
In October '68, during a temporary firing of Weir and Pigpen, a series of Mickey and the Hartbeats shows started at the Matrix - consisting of Garcia, Hart, sometimes Lesh, and any other musicians that might show up, jamming on a few Dead themes and some freeform explorations. Sometimes it's said that they were auditioning for new Dead members, but this is highly unlikely, since the other players were already in established bands. Garcia may have just wanted to open up a new side-project (we'd certainly see more of those in later years). It's less-known that Lesh isn't even playing during many of these shows - with the exception of 10/30/68, these are mostly Garcia/Casady duets. When Elvin Bishop shows up, the Hartbeats take a definite turn towards standard blues jams.
Not all the Hartbeats shows seem to survive - there are some undated fragments circulating - and occasional Hartbeats shows took place into '69, of which we only have the Aug 28 show with Howard Wales.
10/8/68 - Elvin Bishop & Jack Casady
10/10/68 - Jack Casady & 'Marvin' (blues singer & harmonica player)
10/30/68 - Elvin Bishop
12/16/68 - Jack Casady, Spencer Dryden, David Getz
12/24/68 - Garcia with Elvin Bishop, Steve Miller, Harvey Mandel (not on the Archive)
8/28/69 - Howard Wales
Early '69 was a conspicuously guest-free time as the Dead played their limited setlist with Tom Constanten at show after show. As I've mentioned before, in April/May '69 a little setlist upheaval started as the Dead started bringing back bunches of old covers, adding more variety (and sloppiness) to their shows. All of a sudden in late spring, we see a whole torrent of guests taking the stage in Dead shows, which would continue through 1970.
5/29/69 - Santana's drummers join the Dead in the Alligator drum section, and Garcia jams with the percussion; one of them sings a bit in Lovelight.
5/31/69 - Ken Babbs starts Baby Blue with a sad little rap; he's also heard rapping at length after Cold Rain & Snow.
6/6/69 - Jerry is too dosed to play, so Elvin Bishop takes his place for almost the whole show (except Lovelight). Needless to say, we get an extra dose of blues with Smokestack Lightning and Checkin' Up On My Baby. The Lovelight may be the longest ever, at 48 minutes (though some others come close).
6/7/69 - Janis Joplin sings with Pigpen in Lovelight in her usual blues-scat style. (This part of the show suffers from tape deterioration.)
6/8/69 - After an amazing first set, we get no less than two guests - Wayne Ceballos sings Lovelight instead of Pigpen (making it feel twice as long, though Pigpen seems to approve). Then Elvin Bishop (who played guitar in Lovelight) takes over again for a couple blues tunes with Pigpen, Things I Used To Do and Who's Lovin' You Tonight, before Garcia returns.
6/13/69 - Ron Hawkins sings Schoolgirl with Pigpen. Someone plays flute for a bit in the middle of Lovelight, and Ron Hawkins comes back for the raveup at the end.
7/7/69 - Deadlists suggests that Gregg Allman is playing organ in Lovelight. I don't think so - I only hear Constanten - but I'm including it here in case I'm mistaken. (In any case, this was the first show where they met the Allmans, and there was a jam after the show.)
7/12/69 - Madness breaks loose in Lovelight - Pigpen tries to get Mickey to sing, and Weir gives a mike to an enthusiastic audience member who starts shrieking and hollering the blues: "Let me tell you baby, you're a brown cow, let's go get stoned....."
8/3/69 - Very unusual (and anonymous) guests tonight - a fiddle player in Hi-Heel Sneakers, and then saxophone and fiddle in the Dark Star>Alligator>Other One>Caution jam. One of the most unique sets the Dead ever played, though the mix is poor.
8/16/69 - Ken Babbs raps for quite a while after Mama Tried. Someone also raps about the "third coast" at the beginning of Lovelight; this used to be attributed to Babbs, but it is actually some mysterious stranger.
8/21/69 - Charles Lloyd plays flute in Minglewood Blues and China Cat.
8/23/69 - After Pigpen has the crowd yell "Howdy!" he asks for a volunteer: "Anyone wanna come up and testify? - anyone, come up and say something! Y'all chicken?" Some crazed fellow takes him up on it and starts screeching, "Woo-hoo! Everybody get it on! Have a good ol' time! Baby baby, do ya feel it?" and makes a little speech.....
(There are many more Lovelights in '70/71 where Pigpen would give the mike to delirious romantics in the audience. I don't have the heart to seek out any more examples, though.)
9/7/69 - Not the Dead, but Garcia with some of the Jefferson Airplane playing some drunken garage-band oldies from their youth. A rare chance to hear Garcia singing Johnny B Goode (and the first known Big Railroad Blues) - but it's hard to believe he's playing guitar.
9/11/69 - There's a stray audience tape of an early Easy Wind in which Jorma Kaukonen may be playing slide; it's not on the Archive.
10/25/69 - Stephen Stills plays guitar in Lovelight.
11/7/69 - After Mama Tried, someone in the audience plays the Star-Spangled Banner on a pennywhistle, to general hilarity - the Dead respond with a few little traditional ditties.
11/8/69 - In the Caution jam just before the Main Ten, someone recites a little poem in a Dylanesque manner - perhaps John Dawson. (Released on the Dick's Pick.)
12/10/69 - Stephen Stills plays guitar in Casey Jones, Schoolgirl, and Morning Dew, and sings Black Queen. (He probably played in Lovelight as well, but it cuts after two minutes.) Black Queen is excellent.
12/29/69 - Soon after the jam starts in Good Lovin', a disturbed audience member yells into a mike, and they stop for a bit while he's hustled off-stage. This isn't a "guest appearance", but it helps remind us that in many shows (as Garcia occasionally mentions) the stage must have been full of people wandering around - kids, dancers, freaks, and so on.....
2/1/70 - Peter Green plays guitar in Lovelight, and another Fleetwood Mac member hollers for a bit.
2/4/70 - Though it wasn't part of the Dead show, several bands were being filmed at the Family Dog this night; and at the end of the evening there was an "allstar jam" including Garcia, Santana, and the Jefferson Airplane guitarists, part of which was broadcast. It's not on the Archive (or the 2/4/70 Download Series), but it is on youtube.
2/11/70 - For the Dark Star>Spanish Jam>Lovelight, an enormous crew including most of Fleetwood Mac and the Allman Brothers joined the Dead onstage - Peter Green, Duane Allman, Mick Fleetwood, Danny Kirwan, Gregg Allman, Butch Trucks & Berry Oakley.
3/8/70 - A mystery guest takes the mike after Pigpen's Katie Mae and "sings" a blues while Pigpen and the band accompany him - then he continues shouting and tunelessly bleating a harmonica all through Not Fade Away, while the Dead apparently ignore him. This was thought to be Wayne Ceballos; Pigpen seems to have encouraged him onstage, for some reason. (The link has a debate on whether this singer is Ceballos or not - which is ironic, since the genuine Ceballos on 6/8/69 is almost equally atrocious.) Hands-down the worst guest appearance.
3/17/70 - This famed show, where the Dead played with the Buffalo Philharmonic Orchestra, doesn't survive on tape. But there are descriptions of the show here:
(As for lost shows, I should also mention 5/10/70, where the Dead jammed with the Allman Brothers.)
4/9/70 - An unknown guest sings the improvised "Cowboy Song", an interesting Sugar Magnolia-type hoedown, as the audience stamp their feet. http://www.archive.org/details/gd70-04-09.sbd.hanno.6157.sbeok.shnf
6/7/70 - During the Other One drum solo, a lady gives a speech to the audience; not only that, but someone's singing off-mike during the Cryptical reprise. (Deadlists claims this is Robert Hunter.) Someone also sings "hey baby" over the opening of Cosmic Charlie. The Dead themselves, perhaps unsurprisingly, seem a little unfocused.
7/16/70 - At Bear's going-away party, Janis Joplin sings another Lovelight with Pigpen - this one is much raunchier than last year's.
8/19/70 - David Crosby plays guitar in Not Fade Away>Lovelight - unfortunately, in the audience tape it's hard to make him out.
11/11/70 - Jack Casady, Jorma Kaukonen, and Papa John Creach join the Dead during Goin' Down the Road and they play a series of fun jams, blues, and rockers to end the show.
11/16/70 - This Hell's Angels benefit has a few guests on several tunes - Steve Winwood on organ, Will Scarlet on harmonica, and perhaps Chris Wood doing some singing in Not Fade Away. (This show used to be known as 11/23/70, but 11/16 Fillmore has become the accepted date.) http://www.archive.org/details/gd70-11-16.sbd.winters.17361.sbeok.shnf
(There is also a Good Lovin' with Hot Tuna (Jorma, Jack, and Papa John) that used to be attributed to 11/16/70, but it's not on the Archive)
11/20/70 - The bonus set with Jorma Kaukonen and Jack Casady features quite a few hot jams and rockers, in better quality than 11/11.
11/21/70 - Only part of the set exists, a Cryptical>Other One medley. Ned Lagin says this was the first show he played with the Dead, but he wasn't plugged into the PA, so he's quite inaudible.
(Although it's an acoustic set, I should mention here the 11/21/70 Boston radio show they did after this performance - Garcia & Weir played several acoustic songs in which they were joined by Duane & Gregg Allman. This set's apparently not on deadlists or the Archive.)
12/31/70 - During I Know You Rider, you can hear a woman screaming continually for quite a while; the Dead ignore her. After the song, another woman says into a mic, "Um, excuse me, I forgot my cape in the corner over there...." As Deadlists puts it, "Plainly things were a little out of control backstage; perhaps there was a mic live that shouldn't have been." (This is also the show where the Dead direct a spotlight onto an audience taper - Garcia shouts, "There's bootleggers among us - let's find out who these people are!")
12/31/70 - After the Dead show, in the wee morning hours Weir came back for an extra set with Hot Tuna (Jorma, Jack, Will Scarlet on harmonica, Joey Covington on drums) - playing a selection of oldies, most of them in the Dead's setlists, but here done Hot Tuna-style. This is a rare example of hearing Weir (rather than Garcia) as a guest.
Guest appearances dropped off significantly in 1971, as the Dead tightened up their shows. In fact, there were none - except for three nights in the Fillmore East run in April:
4/26/71 - Duane Allman plays guitar in Sugar Magnolia, Hurts Me Too, & BIODTL. He's rather low in the mix (and the song selection could be better) - apparently these songs were almost released on the Ladies & Gentlemen set, but were halted by legal issues.
4/27/71 - The Beach Boys emerge from the mists of time for a little mini-set in the middle of the Dead's set.
4/28/71 - In an even more surprising emergence, Tom Constanten reappears - not for a whole set, interestingly, but he plays in the Dark Star>St Stephen>Not Fade Away medley. This was released on Ladies & Gentlemen.
One summer jam session must be mentioned:
8/21/71 at Mickey Hart's barn - The Dead jam for a couple hours with John Cippolina, David Crosby, Nicky Hopkins & Merl Saunders - and amazingly, it's taped:
12/31/71 also has a raucous midnight start - during the opening Dancin' in the Streets jam, the radio announcer mentions that two men "took off their diapers and are running around the stage nude!" Someone (perhaps one of these men) shouts "Happy new year!" and some random shrieks into a mic during the jam. Afterwards, Weir announces that the stage is a mess....
1972-73 saw a few more guest appearances:
3/25/72 - Bo Diddley plays a set of his songs with the Dead as backing band during the Academy of Music run. Part of it was released on a Dick's Pick (along with the one-time-only Are You Lonely For Me Baby, How Sweet It Is, and Pigpen's last Smokestack Lightning, from the Dead's set) - and a horrible AUD tape is here -
7/16/72 - At the end of the show, Dickey Betts and Berry Oakley join the Dead for a fantastic Not Fade Away>Goin' Down the Road>Hey Bo Diddley. (Duane Allman unfortunately couldn't appear, since by this time he had merged with infinity. By the way, the other two '72 Hey Bo Diddleys were done on 5/23/72 and 8/22/72, which are well worth checking out.)
9/10/72 - David Crosby appears in this excellent show, playing in Dark Star. (He's less evident in the following songs.)
9/30/72 - Several witnesses in the reviews here report a topless dancer onstage - unfortunately, she doesn't appear on the tapes..... But judging by the Veneta '72 film, such sights were common among Dead audiences.
10/9/72 - Grace Slick appears, not topless but apparently drunk - to start the second set, she sings a Janis-style rap while the Dead play a blues jam. She returns to make a little speech about the band before Truckin'.
12/31/72 - David Crosby shows up again to play guitar in the fantastic Other One>Morning Dew jam.
6/10/73 - In one of their giant '73 shows, the Dead give us a famed third set with Dickey Betts, Merl Saunders & Butch Trucks. Interestingly, Garcia picks That's All Right and Takes a Lot to Laugh from his Keystone setlists.
7/28/73 - The encore is the highlight of the show - Not Fade Away, Mountain Jam, and Johnny B Goode with the Allmans and the Band. One of the only times (other than 12/31/73) where you hear Garcia actually playing in a Mountain Jam, rather than just quoting Donovan's melody.
(A joint Dead/Allmans CD set was prepared some time ago from these '73 shows, but release has been delayed indefinitely.)
A new twist came in September '73. For eight shows in the 9/11 to 9/26 Northeast tour, Joe Ellis & Martin Fierro joined the Dead on horns for Let Me Sing Your Blues Away, the Weather Report Suite, Eyes of the World, Truckin' and Sugar Magnolia. These shows have aroused mixed feelings - while the horns added a free-jazz or New Orleans-ish tinge to the sets, some people feel they're more intrusive than enjoyable. It's also notable that the horns weren't added to other jam songs - and this tour in general was rather light on the deep jams. I suspect the horn players weren't given much practice time to work out arrangements - as a result, we get quite a few second-set jams of Truckin'>Eyes>Weather Report.
Though not a Dead show, 11/28/73 is worth mentioning since Garcia, Lesh, and Hart joined Ned Lagin for a Seastones concert - more prolonged and abstract than the usual Dead jam, but more listenable than Lesh & Lagin's 1974 adventures, since Garcia's doing some interesting things.
(This link also includes the 6/6/75 Seastones show, and outtakes from Tom Constanten's Tarot album, also with Garcia, Lesh & Hart.)
Starting on June 23, 1974, Ned Lagin & Lesh played some Seastones pieces in-between Dead sets at most of the '74 shows. These bass drones & synthesizer noises are a bit too experimental for most people; but there were a few times when the rest of the band would come out and turn Seastones into a full-band jam, leading into generally very spacy sets where Lagin could continue playing with the Dead:
9-11-74 Seastones>space>Eyes of the World>space>Wharf Rat
(not on the Archive)
9/21/74 Seastones>Playin' in the Band
10-16-74 Seastones>space>Wharf Rat>space>Eyes of the World
10-18-74 Seastones>jam>Dark Star>Morning Dew
(partially released on the Grateful Dead Movie Soundtrack)
Finally, there are a few 1975 guest appearances:
3/17/75 - Not a show but a session at Weir's studio, in which David Crosby & Ned Lagin rehearse with the Dead on Lagin's birthday - mostly on a couple Crosby songs, Low Down Payment and Homeward Through the Haze. Not one of the more interesting '75 sessions. (The 4/17/75 studio session is also said to have guests - Cipollina, Crosby & Lagin - but I couldn't bring myself to listen. I believe Lagin appears on a number of these studio rehearsals.)
3/23/75 - Ned Lagin (electric piano) & Merl Saunders (organ) join the Dead for this surprising Blues for Allah show. Not only is it a hardcore set to drop on an unsuspecting audience, it's unique in having three keyboardists.
(It's also not on the Archive anymore, since it was on the Beyond Description bonus CD.)
9/28/75 - Matt Kelly plays harmonica on Music Never Stopped and BIODTL. http://www.archive.org/details/gd75-09-28.sbd.fink.9392.sbeok.shnf (sbd)
Once the Dead started touring again, I don't recall any guests onstage until mid-'78, with the likes of Hamza el-Din, Lee Oskar, John Cippolina, and various Pranksters & motorcycles & banjo ladies....but that is a list for someone else to start.