There are many types of mantras, and each is a storehouse of immense knowledge and power Gayatri mantra is defined as ‘gayantam trayate iti gayatri‘, which means the one who protects (trayate) the one who sings (gayantam) is (iti) gayatri.
Mantras have not been made or created, rather they were revealed to the Maha Rishis during their spiritual trance. So the rishis are called mantradrashtas (the seers who ‘saw(drashta)‘ mantra; drashta comes from drishti(vision) ) rather than the mantra kartas (the makers).
It is very important that mantras are chanted in a particular melody, pitch and rhythm because mantra chanting creates specific vibrations in the atmosphere. So each mantra comes with a meter or pitch, like we have talams (adi, rupaka, etc) in classical music. The names of these meters are gayatri (its also the name of a meter), anushtup, trishtup, brihati, pangti, etc. They come with a distinctive time length for each cycle. For example the Bhagavad Gita is written in Anushtup, the Rig Veda is written in Gayatri meter, etc.
Each mantra has a presiding deity. The mantra has to be recited with utmost devotion and love, focusing on the deity in the heart Chakra region. That is why the heart region is touched while taking the name of the Devata.
Beej Mantras and their frequencies:
Mantras have different frequencies and create different vibrations. OM is the sound of cosmic energy and contains all the sounds. The sound that would be created by rotating galaxies is OM. OM is the first and foremost of all mantras. The frequency of OM and other beej mantras are as follows:
OM – 7.83 Hz
Gam – 14 Hz
Hleem – 20 Hz
Hreem – 26 Hz
Kleem – 33 Hz
Krowm – 39 Hz
Sreem – 45 Hz