How to add background music to audio file

hi all,
I am iPhone user.
Is there any professional and voice-over accessible voice recording app which can allow me to add background music to it?
For example I want to record stories and I want to add background music to my voice but I don’t know how to do so and which app shall I use?
Someone advised me to use Voice Memos and for voice recording , then use iMovie app then importing the audio file but didn’t work with me.
Please advise.
Thanks in advance