If you have the Google Play Music extension installed on the Google Chrome then that might be the culprit behind this. If you have other music/media related extensions then use this solution. So, the steps for disabling or changing extension settings will be similar for other extensions as well. Note: Although this method shows the steps to disable or change settings of Google Play Music, this problem can be caused by other music related extension like Plex. This will make iTunes as the default program For example, if you are having troubles with iTunes for Windows, click Music and select iTunes from the list. Here are the steps that you need to take in order to make the targeted application as your default application
In other words, certain applications will become the default applications for your media key usage.