Yes performed in Boston on this day in 1974. This concert and the whole tour were done in support of their most recent album, Relayer.
This tour also served to introduce the public to Patrick Moraz, the Swiss keyboardist who had joined the band after Rick Wakeman quit due to musical dissatisfaction.
The concert only featured songs from Fragile on to the present. The entire Relayer album was featured in the set list, but was done so out of order as compared to the album, with “Sound Chaser” opening the concert (source).
The show has been recorded on radio, and later appeared on King Biscuit Flower Hour. It has not been officially released, and is in circulation online.
I covered Boston Garden here yesterday, in the context of Emerson, Lake & Palmer’s December 10 concert. Yes had already performed there earlier in 1974 on their Tales From Topographic Oceans tour.