James Bongiorno came up with his trinaural processor about ten years ago.
Received rave reviews, won awards and is still very well regarded.
Here is the link.
Trinaural Processor
Can generate a centre channel or play a centre channel from sources such as an SACD.
Am considering it as a possibility for my next upgrade.
I actually have some SACDs that are actually three channel (as opposed to 5.1).
I think these are examples of those three channel master tapes being transferred across to SACD.
If anyone here has a trinaural processor I would love to hear their feedback.
Bruce