Japa Mantras are different from Kirtan, or Invocation Mantras.
From the Yogic perspective, Japa is done internally (silently) with no music, or melody. Each Mantra has a ‘Vedic’ meter, or specific pulse.
With longer Mantras (Gayatri and Maha Mrityunjaya) you can chant vocally in the beginning until you memorize it. Then take it inwards.
Get established in Kriya practice first to familiarize your mind with resting in ‘charged silence’, then bring the Mantra in as the final stage of your practice.
Do not wear the Mala you chant with. It will decrease its power.
Slide the Mala beads using thumb and middle finger. Avoid using the index finger.
Maha Mrityunjaya is the most important Mantra for practitioners of Tantric Hatha Yoga.