What is the ruling regarding one who performs the Adhan (call to prayer)?

Primary text

It is established that Ahmad, upon saying a phrase of the Adhan aloud, would say the equivalent phrase silently. The apparent conclusion from this practice is that it is recommended for the visible part to be the call to prayer and an invitation to the prayer, while the hidden part serves as a remembrance of God the Most High, putting him in the position of one who has heard the Adhan.