ELP performed in Brighton on this day in 1972. The tour was done in support of their latest album, Trilogy. However, due to that album’s noted difficulty to perform live, only two songs, “Hoedown” and “The Sheriff”, were on the setlist. The remainder of the setlist consisted of older material.
The concert has reportedly been recorded, never officially released, and is in circulation online. I say ‘reportedly’ because recordings said to be of this concert are identical to recordings of a concert at the Birmingham Odeon Theatre three days prior. I detail it more here. It’s also worth noting that, at least going off recordings I’ve heard, the ones reportedly from the Odeon are of far higher sound quality. In theory, that could mean that they’re closer to the source.
As of this writing, the Brighton Dome is the single oldest venue I’ve looked at, with an extensive history (some highlights detailed here). It first was built as a stable complex for Prince Regent George IV and completed in 1808.
It was later sold to the city of Brighton by Queen Victoria, and after some reconstruction opened as a concert hall on June 24, 1867. It has since been renovated in 1935 and 1999, most recently opening in 2002. As of 2019, events still go on regularly there (source).
Interestingly for ELP fans, there is a famous old organ on the property which was installed in 1935. It has a great deal of musical range and sound effects available to users, detailed here. There is no historical evidence that Keith Emerson ever used it in-concert, sadly.