Among the more than 360 rules the Buddha gave to monks was a prohibition against listening to music; it was considered to be a possible source of attachment. The result was that only chanting with bells and gongs is performed in Buddhist temples. The Tibetans later added drums and horns. The emphasis in Buddhist chant is to calm the mind and raise the consciousness. Try to feel the attunement of the priest and be aware of what affect the chants and songs have. 

Gate Gate is from the Prajna Paramita Sutra, probably the most important text of Mahayana Buddhism. The Dai Hanna Ceremony is a very ancient chant from the Shingon sect.