It seems to lose 'tracking' or something on a sustained note, kicking down into a synthy type of note without so much dirt on top, then switching back.
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Spector club #243, Rickenbacker #487, Country Bassist #18
A different sort of timbre, but there's this early demo of Sabbath where I can only presume Geezer's bass is going through a guitar amp running flat out: www.youtube.com/watch?v=xD1I-m4jonw#t=4m59s
Not quite as insane as that Megalith, perhaps.
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Brandoni / self-build Precision; Epiphone EB-3 SG Bass; Schecter Model T; one Frankenbass
#136 British Bassist Club