Hi there, Richro65.
I see that you want to remove all of the music from your iPhone. You tried using iTunes, but you're only finding instructions to add to playlist and add to the device. I'm glad to help with this.
Use iTunes to sync your iPhone, iPad, or iPod with your computer -- If you sync your music to your iPhone using iTunes, this article provides the information and steps that you need under "Sync or remove content using iTunes".
When you reach step 3, select "Music" from the left panel in iTunes. Choose "Selected playlist, artists, albums, and genres" under "Sync Music” and make sure that no songs are selected from your library. Click the "Apply" button, and iTunes will remove the songs from your phone.
If you don't sync your songs to your iPhone using iTunes, how do you place music on your phone?
Let me know how that goes, and take care!