The YouTube video features Pat Smear playing the Hagstom Double Neck guitar at 41:43.
In a 2011 interview with Nate Mendel for Bass Player, when mentioned that there are two bassists on the song, “I Should Have Known”, Mendel affirms, "Right. On the record, that’s [Nirvana’s] Krist Novoselic playing bass. Live, Pat plays his part on a double-neck Hagstrom, which is awesome. We’re playing pretty much the same part; I’m just adding some passing notes and following the drums a little, while Pat plays it straight."