I do quite a bit of prayer with percussion, particuarly the Cajon. I have run two workshops on this approach to prayer, at a conference for therapists and pastoral workers, and at a church weekend away. The workshops are highly interactive and last about an hour and a half. They are not the same as a drum circle(!) but introduce a fruitful way of (mainly intercessory) prayer without words. If you're interested in having me to lead a workshop, get in touch.