Is chanting mantras a common practice in Theravada Buddhism? 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?
There is chanting of Pirith. This is not done as a meditation but sometimes advocated to be done when sloth and torpor is preventing you from meditating to raise energy levels. So in a way it can be used as part of your meditation sitting through not exclusively doing this but use it when needed to progress your meditation siting.