iTunes audio cuts out at random times when listening to music This has been an ongoing problem for over a year now. When listening to music in iTunes, something is causing the audio to cut out for a second or two at seemingly random moments. I never stream music. All the music I listen to is stored locally on my machine. I've had the same machine for several years now and it didn't always do this. It used to play music perfectly no matter how many programs I had open or how many labor intensive tasks I was performing. In fact I can recall instances where I was doing some video editing which slowed the machine to a crawl. And even with the spinning wheel of death and everything being frozen, even then, if I were listening to music, it never missed a beat. But now it seems like the least little network activity or the least little bump in cpu usage causes not only iTunes but also audio through VLC Player to cut out. The problem has persisted through more than one complete hard drive wipe and across multiple versions of OS X. Also, I'm not sure if this is related but it seems like the overall output volume is lower them what it used to be. My system in a nutshell:


OS X El Capitan 10.11.4
iMac (21.5-inch, Late 2012)
Processor - 2.7 GHz Intel Core i5
Memory - 8 GB 1600 MHz DDR3
Graphics - NVIDIA GeForce GT 640M 512 MB
750 GB free of 999


I've searched all over the Internet for an answer to this problem and so far I've come up short. If anyone has any suggestions, advice or ideas; any feedback at all would be much appreciated.
I was having this problem with some VBR MP3s I ripped a decade ago with LAME 3.92.  The problem went away when I converted them to fixed rate MP3s in iTunes (File > Convert)  

iTunes 12.4.1.6, Mac OS X 10.11.5