How does this happen?

[edwardofhuncote]

Tangentially related to Jimmy's Steinway piano parable, (which was a fascinating post in itself) the string "afterlength" on upright basses, -this is the length of string behind the bridge leading to the tailpiece termination point- is mathematically 1/6 of the scale length. 7" for a 42" scale bass. This isn't a hard-n-fast number, it's definitely a tunable, customizable thing. Does it matter? You better believe it does. All kinds of weird resonances happen in that 7" and they're troublesome if it happens to clash (or be trying to cancel) a note within the 42" you're trying to play bass in.

[keith_h]

I’m sorry, but nobody told me math would be involved in this thread!   

And science too.

[mario_farufyno]

Sometime ago I got this Strobo Tuner App that displays 1st, 2nd and 3rd harmonics at same time. We all know they are precise and to my surprise I've learned that I can't have all three perfect tuned (the 3rd in particular) so it may be a vibrating string thing. As harmonics are natural and doesn't perfectly match their "tempered" counterpart pitch (or the Fundamental), this mismatch could be the cause of that acoustic chorusing.

I imagine upper harmonics will be out of the tempered pitch even more. The difference is Alembic unveils it better.