Lately, I will go through periods where iTunes keeps opening itself repeatedly. It never plays anything or loads any files or URLs. But I can't figure out what is triggering it to open. Is there a log somewhere that shows why an app opened? Presumably it's due to a file association somewhere.
This is a super old question, but I can admit to giving up looking for a source for a rather long time. It turns out (in my case) that the magic "4th conductor" within the headphone port that is used for the microphone also is used for the remote control. ie: Vol up/down, Play/Pause, Next/Prev, etc. This works by shorting that 4th conductor in various ways. When the cord for my headphones, with only 3 conductors, wiggled in it's loose fit, my laptop thought that I had pressed the play button, which triggered iTunes to open up.
(I have also seen a similar thing happen with bluetooth headphones, as mentioned above.)
I was also experiencing this issue. I had turned off all the auto downloads in iTunes. Then, in System Preferences, I "delete"d iTunes Helper - which did not delete anything and may not have had any effect. I discovered later that it was when I turned on/connected Bluetooth headphones that iTunes opened without any notice in the background.
I haven't found a way around this yet, but at least I know what was causing it.
This was with iTunes 11.4 and OS X 10.9.5
Of course this may or may not be what is happening with your set up. I would be interested to know if other things also cause this.
I just had this problem start up. After an extremely frustrating troubleshooting process, I realized my Mac was accepting commands from my Logitech universal TV remote (which I was attempting to use with my TV). Every time I pressed the OK button on the remote, iTunes would start to play. I had never attempted to pair this remote with my Mac.
As this is happening on my machine, I am guessing it is from a bluetooth speaker connection. As I've disabled any auto updates in itunes and removed the program from startup items. Also turned off any sharing on the computer. OSX 10.10.3 itunes 22.214.171.124. It's nothing really, but it's super annoying.
I have experienced iTunes app opening on it's own, too. I believe the external speaker connection is the culprit as well. Though, I did not have head phones connected, I did have external speakers plugged in.
I realized static electricity from a window fan directly next to my desk may've been responsible for the static & glitch. Avid users know to maintenance computer & auxiliary inputs against dust & static build up (i.e. avoid computer contact with carpet). Static electricity can flow from your finger tips too!
Having lived through reel to reel tape decks to record & playback music, I used my tape head de-magnetizer to eliminate static build up from my computer, screen & cables. I do not recommend using a de-magnetizer because it may damage the hard drive and/or corrupt or erase stored data.
That said, a simpler & safer way to reduce and/or eliminate static charge to your computer & accessories might be to wipe w/ dryer sheet. I can't attest to it's effectiveness but definitely think it's worth a try.