Here are a few interesting facts about the Woodstock festival and the performers.

Some of these are interesting:

--Cancelled appearances--

The Jeff Beck Group was scheduled to perform at Woodstock, but failed
to make an appearance because the band broke up the week before.
Iron Butterfly was stuck at an airport, and their manager demanded
helicopters and special arrangements just for them. They were wired
back and told, as impolitely as Western Union would allow, "****
off".

Joni Mitchell was slated to perform, but her agent informed her that
it was more important that she appear on "The Dick Cavett Show" on
Monday, with its national audience, rather than "sit around in a
field with 500 people" Ironically, David Crosby & Stephen Stills as
well as Jefferson Airplane (who all performed at the festival) also
made it to the Cavett show. It was believed to have something to do
with her breakdown at the Atlantic City Pop Festival two weeks before
where she exited the stage in the middle of her third song crying
because of the fans not listening to her sing. Though Mitchell was
not present, she wrote and recorded the song "Woodstock" that was
also a major hit for Crosby, Stills, Nash and Young.

Canadian band Lighthouse was originally scheduled to play at
Woodstock, but in the end they decided not to, fearing that it would
be a bad scene. Later, several members of the group would say that
they regretted the decision.

--Refused invitations--
The promoters contacted John Lennon, requesting The Beatles to
perform. Lennon said that he couldn't get the Beatles, but offered to
play with his Plastic Ono Band. The promoters turned him down.

Procol Harum were invited to perform but reportedly declined due to
the festival happening at the end of a long tour, and because of the
impending birth of Robin Trower's child; The band elected to pass on
the festival to be back in England for the birth. The child arrived
two weeks late.

The Doors were considered as a potential performing band, but
cancelled at the last moment. Contrary to popular belief, this
occurrence was not related in some fashion to lead singer Jim
Morrison's arrest for indecent exposure while performing earlier that
year; the cancellation was most likely due to Morrison's known and
vocal distaste for performing in large outdoor venues. [12] There
also was a widely spread legend that Morrison, in a fit of paranoia,
was fearful that someone would take a shot at him while he was
onstage. Drummer John Densmore attended; in the film, he can be seen
on the side of the stage during Joe Cocker's set.

Led Zeppelin was asked to perform, their manager Peter Grant
stating: "We were asked to do Woodstock and Atlantic were very keen,
and so was our US promoter, Frank Barsalona. I said no because at
Woodstock we'd have just been another band on the bill." "Led
Zeppelin: The Concert Files", Lewis & Pallett, 1997, Omnibus Press,
ISBN 0.7119.5307.4

Jethro Tull refused to perform; there are varying accounts of the
reasons for this decision. One claim is that they thought it wouldn't
be a big deal[citation needed]; Ian Anderson is reported to have said
he "didn't want to spend [his] weekend in a field of unwashed
hippies". [13] Another theory proposes that the band felt the event
would be "too big a deal" and might kill their career before it
started. [14]

The Moody Blues declined to perform, because they were booked for
another event in Paris at the same time and decided to play there
instead of Woodstock, a decision they later regretted. They were
promoted as being a performer on the third day on early posters that
listed the site as Wallkill.

Tommy James and the Shondells declined an invitation. Lead singer
Tommy James stated later: "We could have just kicked ourselves. We
were in Hawaii, and my secretary called and said, 'Yeah, listen,
there's this pig farmer in upstate New York that wants you to play in
his field.' That's how it was put to me. So we passed, and we
realized what we'd missed a couple of days later."[15]

The Clarence White-era Byrds were given an opportunity to play, but
refused to do so but they did perform at the Atlantic City Pop
Festival held August 1,2 & 3, 1969, two weeks before Woodstock.
Paul Revere & The Raiders declined to perform.

Bob Dylan was in negotiations to play, but pulled out when his son
became ill. He also was unhappy about the number of hippies piling up
outside his house near the originally planned site. [16] He would go
on to perform at the Isle of Wight Festival two weeks later. At his
June 30, 2007 concert at Bethel Woods, the original site of the
Woodstock festival, Dylan joked (just before he performed 'All Along
the Watchtower)': "Great to be back here-- i remember being here,
playing at six in the morning, and it was pouring rain, too... a big
field of mud!" [17]

Frank Zappa and The Mothers of Invention Quote: "A lot of mud at
Woodstock. We were invited to play there, we turned it down." - FZ.
Citation: "Class of the 20th Century", U.S. network television
special in serial format, circa 1995.

Free were asked to perform and declined.

Spirit were asked to perform but declined and went on a promotional
tour.