iTunes starting by itself and playing music

I've been having this problem and solved it. While I was looking for a fix, I've found that it is a common problem and the cause can be pretty much anything. I thought it would be a good idea to list potential causes for this problem for future reference. Feel free to complete this list if I've missed anything.

Here are some of the possible causes for iTunes starting up / playing songs by itself :

• Other applications may be requiring access to iTunes' database, try disabling music-related apps or plug-ins (i.e. Last.fm)
• iTunes may be set to start up when you plug in an iDevice : in the device summary page in iTunes, untick "Open iTunes when this device is connected"
• If your Mac has an IR receiver, it may be receiving signals from a remote (controlling another Mac) : in system settings, under Security / Advanced... disable the IR receiver or pair it with a single remote
• An iDevice might be using the Remote application for iOS to control your library via wi-fi. In iTunes settings, under Devices, click Forget all remotes
• Some Macs (or all, I don't know) have audio jacks designed to be compatible with Apple's iPhone earphones, so that you can control your system volume and iTunes music with the buttons on the earphones. If you have them plugged in, check that you are not accidentally pressing them. If you have external speakers or any other headphones plugged in the audio jack, make sure it is correctly inserted because a loose connection could create "noise" which your Mac might interpret as a play/pause signal.

If nothing else works, you can try starting the Activity Monitor (under Utilities or System, not sure) and ending iTunes Helper process. This *might* solve your problem, as one of iTunes Helper's purpose is to start iTunes automatically when required. Ending it is not recommended as it is supposed to always be running in the background but it may solve your problem if nothing else works.