In Mahayana Buddhism chanting mantras is one of the core practices and each mantra is associated with a certain Buddha form (yidam).
Since in Theravada Buddhism there is no meditations on yidams (or am I wrong?), I'm wondering what is the role of mantra chanting. Are there secret mantras which can be recited only after receiving the transmission from the teacher or can the mantras be shared publicly and used by anyone? And finally, are prayer beads (malas) commonly used?