A good practice is to sing. How wonderful sound is.  It is the subtlest vibration, and because of that mantras are also sounds - but they are inner sounds.  

An article in the Journal of Behavioral Medicine titled 'Good health going for a song' of 20 January 2004 had this to say:

-
SINGING strengthens the immune system, according to research by scientists at University of Frankfurt in Germany, published in the latest edition of the US Journal of Behavioral Medicine.

The scientists tested the blood of people who sang in a professional choir in the city, before and after a 60-minute rehearsal of Mozart's Requiem.

They found that concentrations of immunoglobin A -- proteins in the immune system which function as antibodies -- and hydrocortisone, an anti-stress hormone, increased significantly during the rehearsal.

A week later, when they asked members of the choir to listen to a recording of the Requiem without singing, they found the composition of their blood did not change significantly.

The researchers, who included Hans Guenther Bastian from the Institute of Musical Education at Frankfurt university, concluded that singing not only strengthened the immune system but also notably improved the performer's mood.
-