AC/DC - Go Down - Live 1977 (Very rare)
Marana Civic Center, Hurstville, Australia - February 5, 1977
The band was finishing up on Can I Sit Next To You Girl, when Malcolm suddenly decided to take a different direction, a very familliar sounding direction.
You can hear the backing riff of Go Down being played by Malcolm, and Angus at some point, nearing 40 seconds in this video, starts playing the, what would become, guitar solo of Go Down. This is weeks before the sessions started for the Let There Be Rock album, which was recorded in Australia after this tour. Vocals aren't present, as Bon hadn't written any vocals for the track yet, or wasn't satisfied with them at the time.
This is honestly fucking amazing :)
Image source: http://www.highwaytoacdc.com/index.php?articleid=1063