Watch the The Mother Of Bass online guitar lesson by Jasper Mortier from 50 Blues Bass Licks You Must Know
For listening to great upright players just start before the electric was invented (i.e. early 50-ies). The swing era (30-ies 40-ies) is a good place to start; Benny Goodman with Charlie Christian for instance. Slam Stewart with Slim Gaillard in Slim and Slam is killer. And the start of R&B in the 40-ies, with Louis Jordan and T-Bone Walke. Great examples of unbelievable bass players. And most of the blues stuff in the early and mid 50-ies was done on the upright: Big Daddy Crawford with the early Muddy Waters days played some of the best upright bass ever, as far as I'm concerned. Very nice slapping too. And a bit later all of the Chess material; often with Willie Dixon. So that's not only Muddy Waters, but also Chuck Berry, Howlin' Wolf, Jimmy Rogers and Little Walter. Old Johnny 'Guitar' Watson from the fifties is great too and the first recorded BB king songs from the early 50-ies. Note: all of these recordings were done totally acoustic, so no bassamps and no piezo pickups. If you pluck the string, the string is limited in it's movement by the fingerboard. That's why it sustains less. Normally you'll pluck more parallel to the fretboard resulting in a string that can move more freely. But there's also a pickup issue. Without getting too technical; this plucking doesn't work on electric, because the string will move less in and out of the magnetic field of the pickup. Thus there will be less output. Acoustically that doesn't matter of course and a piezo pickup - like often used on the upright - picks up changes in pressure. So for these kinds of pickups that's no issue. A very commonly used pickup is the Underwood with two pickups in the slots on both sides of the bridge. If you use only one pickup (mostly on the E-string side, so just take out the one on the G-string side) you'll get a much more fundamental tone with less overtones. This could suit your way of playing. There's a lot of brands supplying just one pickup instead of two.