Can stable and unstable be installed simultaneously?

["J.B. Nicholson-Owens" <jbn forestfield org>]

I'd like to have both EasyTAG stable and unstable installed 
simultaneously on the same GNU/Linux system so I can more easily test 
things across versions without having to uninstall and reinstall.

I understand why I can't run both versions simultaneously, and I won't 
run both versions simultaneously, but I'd like to have them both 
available to me for easy testing and upgrading using the system upgrader 
(apt-get).

I tried enabling both repos:

http://ppa.launchpad.net/amigadave/easytag-unstable/ubuntu
http://ppa.launchpad.net/amigadave/ppa/ubuntu

but that always leaves me with one version that has the highest version 
number (always the unstable) currently 2.3.5-0amigadave1.

Is there any way I can get them installed so they co-exist on the same 
installation?

Thanks.