I'm not sure if this is a launcher or game-based bug, but it doesn't seem like intended behaviour.
How to reproduce:
1. Load up a game and alt+tab to the desktop
2. Start windows task manager and close minecraft from the tab "applications"
3. Minecraft disappears from the tab and taskbar, but game sounds can still be heard and "Java Platform SE binary" can still be seen in the "processes" tab in task manager. Can be repeated to cause a cacophony of game sounds.
Linked issues
is duplicated by 1
relates to 2
Comments 11
No, I had never even heard of it before searching just now. I don't see how it could have any effect in a single-player world though.
Looks like a regression of MC-1408
Not totally similar, I was able to terminate the javaw.exe normally at any moment. It also only happened if I closed minecraft through task manager, not after normal exiting.

Java 1.7.0_17
Your Java version is ancient! Please update your Java to the latest version (1.7.0_55 / 1.8.0_05): http://www.java.com/en/download/.
When using a 32-bit browser on a 64-bit operating system the automatic version detection will only show the 32-bit version of Java, the 64-bit version needs to be downloaded manually: http://www.java.com/en/download/manual.jsp.
I upgraded my java to 1.7.0_60, apparently it was old because I use chrome as by browser and it doesn't have a 64-bit version. It didn't fix the problem however. I still get the exactly same behaviour when closing down minecraft, even though the launcher clearly states that the java is upgraded.
As for two separate processes, I can only see one: http://goo.gl/7XKyns Maybe there is a difference between os-x and windows, but what I expect is that when selecting minecraft and clicking "end task" the whole program would terminate. But afterwards I still can hear game sounds and see this in the processes-tab in task manager: http://goo.gl/8f6z46 (sorry for the finnish ui)

Edit: hm, seems your right. Regardless, this would be a java or task manager issue

Related to MC-59806.

Is this still a concern in the current Minecraft version? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases. If this has been done, we can reopen the issue.
Keep in mind that the "Resolved"-Status on this ticket just means "Answered", and that we are waiting for further information on whether this issue still exists or not. We will reopen it as soon as the requested information has been delivered.
Ticket resolved as incomplete, because no answer in a reasonable amount of time (1+ year), if it still happens, please update the ticket.
Do you have K9 installed?