Mantramu yantramu and tantramu
Omkaar is three types. They are: Mantram Yantram and Tantram.
Sound is known as Omkar. This is the root cause of this Creation. Omkar is called Nada Brahmam.
This Omkar is the first and foremost mantra. The root cause of all other mantras is this Omkar only.
Man traayate iti mantrah= This protects the unsteady mind. As such Omkar is called Mantrah.
Yan traayate iti Yantrah= Machines requires energy to run. Likewise this protects the decaying body by providing energy. . As such Omkar is called Yantrah.
Tan traayate iti Tantrah= To keep the energy one body is required. This Omkar protects the energy by providing a body to keep that energy provided by IT. As such Omkar is called Tantrah.
Hence Omkar is mantra, Yantra, and Tantra.
All others are replicas only.