[another Jamerson fan here]: I've read where Jamerson refused to clean his strings "to keep the funk in". Well, if your strings are really clean, new, round wound and smaller gauge, then the ringing open string tones will sound noticeably different from the stopped tones. But Jamersons strings, being "funked", would sound very similar whether they are played open or stopped, especially if they are old. Also, his Precision bass had a rubber strip glued to the bridge cover that just touched the strings enough to stop open-string ring. As most upright bass players, he was an artist when it came to open strings to drop in notes, keep in tune, and use dead thumping notes. If you check out "Marvin Gaye "What's Going On / What's Happening Brother"" on YouTube at 1:23, 2:24, 2:55, and 7:49, you can see his single index finger "Hook" style pizzicato, just forward of the pickups, and perhaps how he used his thumb to mute open strings. Also, according to Bob Babbitt, he had a light touch with his plucking - especially to allow raking - and I'm sure the B15N Ampeg and heavy gauge LaBella strings had a big say in his tone, too. Many will try to sound like James Jamerson, but no one will duplicate him as a lot of his sound was based on his personal reaction to the music he was immersed in. Anyway, he died too young. After Jamerson, Motown morphed into something completely different. It's ironic that his bubbling, velvet like bass lines last forever while all the pop and slap schtick that replaced him is basically unusable in ensemble playing - unless one wants to be the star woodpecker all night.