They are taperwound & I guess they are Elixirs, though not certain, as I took them off my 2nd hand but hardly used SR506 & put them on the Aria as I needed to lower the action more than the bridge would allow, which the taperwounds afforded. These strings, which are quite new sounding, didn't cause any trouble on the 506 up high so I don't think it's the strings but.... Also, on this Aria bass, the strings feel kinda tight & stiff, even the original set, not the same as any of my other basses, Warwick Thumb BO 5, Ibanez 505 & 506, Steiny 5, Jazz basses, they all feel 'softer' to play. The Aria's strings seem quite taut. Lowered the single MM pup but can still hear the tritone thing unplugged so I guessed it wasn't the pups.
It starts on all strings bar the G & gets more obvious as I move up to the 24th. I've never experienced anything like this in 32 yrs of playing, & haven't heard of it either. I use very low action but play with a very light touch, ala Gary Willis, so I expect some buzz at times but this is a conundrum!
Thnx for the ideas though, guys
. Bought an Aria IGB68/5L, a rare bird, & after lowering the action, truss rod straightening, string change to taper-wounds so I could get the action lower as the bridge wouldn't let me go any lower, this bass has some nasty, b5 overtones 
happening on the D, A & some E string notes around the 14-24th frets. No particular pattern or consistency, as in buzz & the like, just a clearly 'out of tune' unintended double stops that sound very 'Twilight Zone meets Aliens in Roswell-ish', 
