OK, so I have solved the issue.
This will work for any tablet that does not have an external SD Card.
Go to the play store and purchase StickMount. It costs about £1.50. Go onto amazon and buy yourself a USB OTG cable. That'll cost you about £3. Now buy yourself a nice big USB flash drive. Copy all your music to the flash drive. Plug it into the USB OTG cable and plug that into your Nexus 7.
Now when StickMount mounts the drive, in teh options select that a media library scan should be performed on the drive when you plug it in.
All the music on teh drive will now be included on the local library.
Open up Amplifi remote and go to the music library section and there is all your music.
Next play a song and sigh in disappointment as you realise that instead of using some sort of hugely clever sound matching algorithm to find an appropriate tone from the Line 6 custom tones catalog, AmpliFi remote simply gets the name of the artist that is currently playing and does a search for that name in the catalog, something you could quite easily do yourself in the search tab.
Still, I beat Google and that's what counts.