Studer 1 194 533. 90 degree shifter. LTspice file

[KA-Electonics.com]

The increase in I+Q level from L-R contribution is highly program dependent.
The range appears to be 0 dB for mono inputs to +3 dB for uncorrelated noise.

There's a Zappa song called, IIRC, "America Drinks and Goes Home" where L and R are virtually independent recordings. Pretty sure that one would rise 3 dB like Shape of Things.

On the guitar sample its more of a width enhancement/stereo synthesis than a positional effect.

 

[abbey road d enfer]

The increase in I+Q level from L-R contribution is highly program dependent.

Indeed!

The range appears to be 0 dB for mono inputs to +3 dB for uncorrelated noise.

Seems to corroborate theory.

On the guitar sample its more of a width enhancement/stereo synthesis than a positional effect.

Exactly. After all, that's the idea behing stereo synthesis. I guess it's possible to use it in conjunction with good old panning (or phse-shift steering) for positioning.