Thanks der_bud, The link you sent is dealing with a slightly different problem. Opening Audacious for the first time always opens the ///Trash folder. If you select another folder and then close audacious and re-open it, then it will open in the last selected folder. If you now close audacious and open ///Trash from the Panel applet, then audacious will again start in the ///Trash folder. I've tested this in Siduction and Mint 17, both with Cinnamon. This is clearly an Audacious bug.
My problem is quite the opposite. Using the panel trash applet causes Audaciuos to open in both Siduction and Mint 17 Cinnamon. The applet is trash@cinnamon.org which I don't think is used in the Mate desktop you linked to.
It's not a fatal problem as a user can either drop audacious or the applet but I reported it as audacious is included by default with Siduction and
the developers may want to be aware of the bug.
Cheers