Wikipedia
Jagar ( Devanagari: जागर) is a form of ancestor spirit worship practiced in the hills of Uttarakhand, both in Kumaon and Garhwal. The word Jagar comes from the Sanskrit root, Jaga (meaning to wake), Jagar is a medium or way in which Gods and local deities are called or waked from their dormant stage and asked for favors or remedies for certain problems plaguing the person.
It is attached to the idea of divine justice and is organised to seek penance for a crime or seek justice from the gods for some injustice.
Music is the medium through which the gods are invoked. The singer or Jagariya sings a ballad of the gods with allusions to the great epics like Mahabharat and Ramayana and which describes the adventures and exploits of the God being invoked.
These traditions are the part of a kind of Folk Hinduism prevalent, in fact, all across the Himalayas, which have been there along with the mainstream Hinduism for ages.
The hard life of the Himalayas and constant exposure to the vagaries of nature inspired a strong belief in paranormal phenomena and also in numerous Folk Gods who were given great reverence and respect. Every village had its own God protecting its boundaries called Bhumyal or Kshetrapal, each family has its Kul Devta or Kul Devi and numerous other benevolent demi-gods/goddesses and malicious spirits which could reward or torment people and had to be appeased.
The isolation of the Kumaon and Garhwal Himalayas promoted the emergence of local religious traditions which are still strong in these regions along with mainstream Hinduism
Jagar ceremonies are of two types one is the Dev Jagar, the invocation of a god, usually local gods in the body of the medium and the other is the Bhut Jagar the invocation of a deceased person spirit or soul in the medium’s body, although other forms like Masan Puja also exist.
Today, Jagars are seen more as cultural and musical heritage in the need of preservation than the religious ceremony itself. But it is still highly revered especially in the rural areas and the New Delhi also, because lot of Kumauni and Gadwali lives in Delhi so they can not go to villages every year for jagar so they started Jager in Delhi also , the main god of Uttrakhandi people (Bhairo , Gweil, kature, Bhumia, Ramoul, Kalbisht, Narsingh, Ujayibeer, Naag, or more. These are the strong power which exist on this planet but the power comes on the human body when jager start. The all the power lives in our universe. The jagar shows that the Hinduism is oldest religion on this planet, the jager always happen in same way as it started thousands years ago in Himalaya in three languages Sanskrit' Kumauni, Gadwali. in terms of science we can say the power comes in human body from other planet.
For years of evolution Jagar singing has transformed into an art which is greatly cherished and the exponents of which are often heralded as living heritages.