Instead of smooth jazz at night, I suggest KOY follow the lead of the venerable Lumberyard 1440 and shut 'er down at sunset. At least Phoenix area DX'ers will have a shot at hearing what some out-of-market programming giant will have cooked up for his 1230 flamethrower.
Having killed the carrier once or twice on that 1230 transmitter myself, I can say with certainty that the only thing you'd hear on 1230 if it were to go off at dusk is the unintelligible sounds of at least 2 or 3 stations stepping on each other.
It's any wonder that you can get KOY after dark at all amid all of that mess, although having a 5/8th wave tower probably is a big help.
At one point in the 90's, Jorgy studied selling off the Buckeye property and diplexing 1230 off the 550 stick, but moving to 48th & Southern would have made the night signal so bad that it wouldn't cover enough of Phoenix to keep the city of license. It would have covered enough of Tempe to qualify changing the COL to that city, but ultimately it was decided it wasn't worth the effort. Ultimately, we gave the Phoenix Police keys to the building so beat cops could use the bathroom and write reports in the old KRIZ office.