I want to remove all songs from iPhone 5, have unchecked and synced but iTunes still says I have 5GB of audio! I always thought I knew a fair amount about iPhones/iTunes etc but this has me stumped!

I have a 16 GB iPhone 5 running the latest version of iTunes on a Windows Laptop. I do not have iTunes Match. 

Due to having 100gb of music on the laptop I have already 'checked' the following options in the iPhone 'summary' 


Sync only ticked songs and videos
Manually manage music and videos


I then went into 'music' and unchecked all the artists, albums etc to the point it said 0 songs (in light grey next to where it says sync music)

So looking at that it should mean I have no songs selected, so none on my phone... but no! 

It is still telling me I have 5gb of audio! I have gone back and forth applying​/syncing​/checking​/unchecking in the hope I have overlooked something but I am now totally stuck on what to try next.

All I want to do is remove all songs from the phone and then put some fresh music back on.
Assuming you're running the latest iOS (iOS6) 

From the Home Screen, go to Settings > General > Usage

Wait while it loads your apps, then select music. 

Then tap 'Edit' and delete your music.