That is weird.......but I doubt it is in the radio because it only happens on 123.5. Bet you have something on that freq or a harmonic of 123.5. I remember hearing music on 123.3 in the California Central Valley, but only in certain areas. I remember flying my primitive RC model on 27 Meg's, near the base comm center. I was transmitting a series of beeps ( one beep for left, two beeps for right, when an airman came running out of the comm center shouting I was all over 243 emergency freq. I didn't believe it, so he invited me to come in and listen........ Sure enough, I was loud and clear on 243 which is the ninth harmonic of 27 Meg's)
Good luck,
JJ