How to delete individual songs from the Music App on your iPhone or iPad
- Launch the Music app on your iPhone or iPad.
- Find an individual track you'd like to delete and swipe your finger across it to the left.
- Tap on the big, red Delete button to remove the song.
- The song will now be off your iPhone or iPad and your storage will be freed up.
That's all there is to it. The tracks that you deleted will now be removed from your iPhone or iPad.
If you're using iTunes Match you'll see a cloud icon next to a track indicating you can download it again whenever you'd like. Otherwise, you can plug into iTunes whenever you'd like and re-sync your music again whenever you'd like.
Source : imore