Is it permissible to listen to audio recordings of my deceased father that contain national songs he recorded in his youth, knowing that he repented sincerely before his death?

All praise is due to Allah, who guided your father to repentance. We advise you to be dutiful and good to him.

Singing is of two types: permissible and forbidden. The permissible type is that which is not accompanied by musical instruments and whose lyrics are free from obscenity and anything that contradicts the Shari'ah.

As for that which is accompanied by musical instruments or contains obscene language, it is not permissible to listen to it, and any such singing on the tape must be removed.