Warthur
Released in a rush as a "Beat the Boots" measure by Crimson - an inferior audience tape of the same gigs had been circulating on CD at a frankly absurdly inflated price - B'Boom is derived from the soundboard tapes and was thrown out onto the market in a hurry without much tidying-up for the sake of suppressing the bootleg release. As such, the sound is good, but not top-notch quality.
It's notable that whilst this release is included on the THRAK boxed set, it's as a little extra something on one of the Blu-Ray discs, and the boxed set puts more effort into showcasing other live gigs from this particular Crimson lineup. Ultimately, this was never intended for public release, and was only put out on the market because someone decided that they wanted to misuse their personal taping of the gig to royally rip off King Crimson fans.