Look up "Musical Hallucination". This is not unusual, esp with brain injury. There may be a connection with fall; there may not be. Speak to the doctor about it. Much information online.
Kelly, does your Mom wear a hearing-aid? If yes, it could have been jarred in your Mom's fall. My Mom use to hear talk radio when she first got her hearing aids... the hearing aids were adjusted and the radio was gone.
Speak to the doctor about it. Much information online.
Best wishes to you and your mom.