Remember the saying that music calms the savage beast? It calms the savage baby, too.
I once cared for a three month old little girl. Her mother had not left her before. She answered my ad and asked me to come sit with the baby so she could play tennis. Each time mom would leave, the little girl would cry the entire time her mother was gone. I would always sit and patiently hold her because I knew she was scared.
One time I noticed a transistor radio and so I picked it up, turned it on and tuned into a music station. As soon as the music came on, I mean immediately, this little gal stopped crying. She looked at me and she looked at the radio and she looked back and smiled. From then on we were best buddies. Her mother was amazed that something so simple could soothe her crying daughter. She was relieved that she could go play tennis and not worry or feel guilty about leaving her baby with a sitter.