Iphone slow reading USB harddrive

After watching 1 the videos I bought an aero just so I could use my 500gb harddrive which is full of music which has already been through rekordbox and I wanted to use my iphone as a browser through the rekordbox app, my problem is when I access my files which are put into playlists my phone just keeps freezing then slowly but surely loads on the decks but as you can imagine this is very frustrating and was wondering if there was anything I was doin wrong thanks for any help