Kirtan Kriya is a chant (Sa Ta Na Ma) with mudras (thumb presses against index finger when chanting Sa, then presses against the middle finger for Ta, and so on).

I love all chants for their brain and emotional cleasing powers but this particular chant has been researched using SPECT scans.

This article, Yoga Journal, 2005, explains the benefits.  Don't you love the subtitle, Yoga for Age Proofing Postmodern Minds?  In this study, the participants chant for 12 minutes but even 7 minutes brings noticable calm.

I like to use music when I chant and recommend this music, Sa Ta Na Ma by Snatam Kaur.