The Sanskrit word “japa” refers to singing a mantra repeatedly or a mantra. Japa is another word for meditation that is done with a divine object as the primary focus. Also known as a rosary for the soul. The 108 Japa chants are performed all at once as a set. Its an ultimate tool to meditate and helps one to concentrate and focus in the repetition of the mantra.
Japa being upamshu, soft recitation seems to be more effective.