Though a heck of a lot of people got to witness the monster festival that was 1969's Woodstock, a notable exception was Joni Mitchell.
Famously, her agent thought it would be a better idea for her to keep her scheduled appearance on the Dick Cavett Show, and so Joni barely missed one of the most celebrated and fabled musical festivals of all time. Upset about not being able to attend, she quickly wrote the eloquent and apt song "Woodstock" based on what others had said about the festival, capturing a moment at least as well as any musician who was actually there.
Growing up in a Crosby Stills Nash Young-heavy household, we never ever listened to Joni Mitchell's version of her own song "Woodstock" at all. I didn't even know she had written it when I was young. Finally, in college I started listening to her music and found her version to be much more haunting and moving than the comparatively light and sunny (and kinda wanky) CSNY version.
Here she is playing the song at a festival in Big Sur in 1969, just one month after Woodstock. I believe this is the first public performance of "Woodstock" ever. As she says, "Well everybody has heard about Woodstock and maybe a lot of you were there," you can hear the utter regret in her voice. It's a gorgeous performance.
Here's the CSNY version, in case your memory needs recharging: