Emerson, Lake & Palmer performed on this day in 1973 at Boston Garden.
This show was a stop on the Brain Salad Surgery Tour, during which Brain Salad Surgery was played in full as part of the set nightly.
No reviews of the concert are readily available that I was able to find online.
A recording of the concert exists that has not been officially released. It is in circulation online.
Boston Garden, the venue at which they performed, was primarily a sports venue which hosted both the NHL’s Boston Bruins and the NBA’s Boston Celtics. It first opened on November 17, 1928 and seated 14,448 (source); other sites state its capacity was 13,909 (source). Infamously, the building was not air conditioned (source), meaning ELP would have worked up quite a sweat despite performing in Boston in December!
Music history-wise, the Beatles famously played here in 1964 while on their first tour in the US, filling the auditorium. Sadly, the building was closed in 1995 and demolished in 1998.