Out of Balance

Spot on! A couple of years ago I noticed my system was definitely out of balance.

Yes I checked the cables replaced tubes. Went as far back as having the manufacture test the preamp. I ran my DAC through the amp and still missing part of the sound in the right speaker. 

A friend was having a Party and asked if I would supply the music . I brought over my Allen & Heath mixing board along with my Yamaha Powered speakers and Focal subwoofer. Sounded great not a problem after I adjusted the Pan control.

Playing music now through my regular system and use the balance control every now and then. 

Thank yo for bringing this to attention . This is equivalent to hearing a hum in your speakers finding out you have a ground loop after you paid good money to send your system out for testing

This is simply another recording variable, strange mixes aren't that unusual. Trying to 'repair' these mixes on an individual basis is a recipe for unhappy listening sessions so I just accept them as is.

Well, the whole point of my post was quite the opposite.  A quick twist of the balance control took an annoying recording and made it quite wonderful.  Why in the world would you want to "accept them as is"??

It's window on the artist's power in the recording studio, or the engineer in the mixing box at a live event, with the artist's final approval. Of course very old recording quality may be limited for tech reasons.

Best example I like is Stevie Nick's Crystal Visions CD. Perfection in studio and live. 

To me adjusting tone controls would be like opening a bottle of wine and adding things. I prefer to take art on the artist's terms.

+1, @elliottbnewcombjr  !

I will add that many pop and rock recordings made during coke-fueled years (1970-1990) are off balance as well.  My McIntosh pre has remote balance control with a very large range.  It is my "soundstage centering control."