Question

Sounds can be recorded on tape.Why must the coating on the tape be between soft and hard magnetically?

Answer 1

Coating on the tape is between soft and hard because of the coercivity.Coercivity means the material are very resistant to become demagnetised. If coating is hard , then coercivity is high then it become permanent magnet, if coating is soft then , coercivity is less so material can loose its magnetic proprieties easily.
So we keep the coercivity in between the soft and hard.