Is there a application/synchronization (not entirely sure what I am supposed to look for) that makes it possible to play music on my ubuntu desktop and then change/pause/play it with my Android phone? Maybe something were I connect with bluetooth?
I am not looking for a while VNC or remote control just simple music play!
There are quite a selection of Android remote controls for a popular music players running on Ubuntu.
Rhythmbox
Remotebox on Google Play
Rhythmote for download from the project's homepage
VLC
XBMC/Kodi
Official remote application Kore from Google Play
The remote applications vary considerably in their feature support. Which to choose depends a lot on personal requirements.
For me the combination of Kodi and it's remote app works very smooth, covers a lot of player controls, and has the nice feature of displaying cover art of tracks playing.