Brass and string instruments are designed to play perfect fifths, and the players can control the pitch so that whatever notes they are playing are in tune with each other--

As to the synthesizer, one of the things that can be adjusted is the intonation--the possibilities are completely unlimited--the only thing is that you would have to adjust the pitch of each key and create patches, unless you can find patches and banks for the tunings that you want somewhere on the web--there are mail lists for users of different types of synthesizers, and often the people on the lists are professionals who spend their days sitting in a big studio, programming etc, so they can help with this-- Sometimes, the people on the list even developed the synth you are using--

Peter T--everybody has good listening abilities--it all depends on what you are in the habit of listening for--

Dennis Sandoli, who is reputed to be the greatest guitar and Jazz teacher in the known world, seems to sit his students down and make them pluck each of the open strings and listen to them, over and over again--