Here is the description of my new app TagExplorer:
Compatible with iOS 5, 6, 7 and 8
TagExplorer is the first and only app that lets you change the id3 tags for songs in your iOS music library directly on your device. Simply select the song you want to edit the meta tags for, and then you can change the title, album, artist and album artist for that song.
TagExplorer will create new artists, albums, or album artists if necessary. In addition to being able to create new albums or artists, TagExplorer also searches for existing albums or artists and uses those instead of creating new entries. You can also choose to change just the details of the current song, or for all matching songs (e.g. album name for all songs in that album).
This app works with music from iTunes match as well as music imported with the popular music importing apps in Cydia (including AudioExplorer+), as well as music from iTunes (purchased on-device or synced). It can even change the tags for videos, podcasts and audiobooks.
As this is an app and not a tweak, it runs without any dependencies and therefore is very stable. It has been tested by diligent beta testers running different devices and iOS versions. The app even works in the iOS Simulator!
Please note that unless the item you’ve changed is going to sync back anyway, changes do not appear in iTunes (you may also need to adjust some sync settings to stop iTunes from erasing the changes upon syncing, or use selective sync or even turn off music syncing). Also, please note that the tags of the individual music files are not changed, just the music database entries.
And the icon (not rounded):