Is it permissible for a singer who performs in immoral parties and also gives the call to prayer (adhan) in the mosque to continue giving the adhan, especially since the Imam is aware of his behavior and he is not an employee of the mosque?

If the mu'adhdhin (caller to prayer) is an immoral person who sings in corrupt parties, his adhan (definition) (call to prayer) is disliked (makruh (definition)) but sufficient (mujzi') according to most scholars. However, his report alone should not be relied upon for the entry of the prayer time, because the report of an immoral person is not acceptable. The complete qualities of a mu'adhdhin are justice and knowledge of the prayer times. Scholars have differed on whether these are conditions for the validity of the adhan. Those in charge of the mosque should arrange for an upright mu'adhdhin, and advise the immoral mu'adhdhin to repent.