''Naubat Khana'' (Drum House), an important Mogul architectural element- Red Fort, Delhi

Naubat Khanna, Red fort Delhi commons.wikimedia.org

Delhi:Naubat Khana and red fort before 1857.en.wikipedia.org
Above image: The Naubat Khana and the courtyard, before its destruction in the 1850s by the British colonialists. The vaulted arcade of the Chhatta Chowk (long passage that has a bazaar) measures 540 x 360 feet, and ends in the centre of the outer court. The side arcades and central tank were destroyed following the 1857 rebellion (apparently during the siege of Delhi) ...................
Naubat Khanna, Red fort DelhiYouTube
 Inviting Royal guests or other important dignitaries by the ruler/head of a state (host), as tradition has it, requires certain protocol norms. In the early period, before the arrival of the Europeans, almost most of the  palaces built by the Indian rulers - Maharajahs and Nawabs in the northern states had a drum house at the entrance to invite the dignitaries and their retinue with honor and dignity worthy of them. The drum house or Nausat Khana  was also used to announce the arrival and departure of the ruler from the fort or palace. During the Mogul rule the drum house  had a specific design - a fusion of Muslim and Hindu design style. Simple and impressive, they never failed to attract the attention of the people.  

Naqqar Khana or Naubat Khana (Hindi:/ Urdu) refers to a special  drum house or orchestra pit that normally becomes very active during  ceremonies. Colloquially speaking,  it is a drum house  (Naqqar/Naubat)-house (Khana) and was part of a distinct Mogul architectural feature.  It was built in many places in the northern Indian states that were under their control.
Interior. Naubat Khanna, Red fort Delhi  Pixelated Memories
The famous Naubat Khana is in  Red Fort, Delhi where this pavilion is close to the entrance on the eastern side of the ten pillars lane. Adjacent to it was  a different pavilion where royal palanquins and other paraphernalia were placed. In those days the 
the royal entourage was so grand and and attractive, playing on numerous musical instruments  on certain occasions was part of the royal protocol. The Naubat Khana used to house as many as 18  musical instruments  for entertainment.

Constructed in 1636 CE by the Moguls,
the Naubat Khana in the Red fort was paid least attention  after the decline of Mogul rule;  it was the end of their  patronage. This beautiful simple architectural piece of work fell into disuse and consequently it remained in a state of neglect for a long time - roughly a century. 

The credit goes to a British official one  George Fisher who found it fascinating and  took keen interest in Naubat Khana structure  and restored it in 1858 to house the new Zilla School (district school). After India's independence in August 1947, no attention was paid to revive countless monuments because of the new Indian government 's preoccupation with financial constraints, etc. When the British left India, the new government led by Pandit Nehru, was heavily burdened  with a poor country with almost empty  treasury, abject poverty and impoverished population. Besides, India was pushed into a chaotic situation when negotiations were  on with countless princely states  to join the Indian union. There were some recalcitrant rulers like the Nizam of Hyderabad who was misled by some in this side to join Pakistan.  Therefore, after the end of British Raj, the place became dilapidated due to lack of funds and priority. The government used it as the police headquarters for some time.

In the Mogul days, musicians from the Naubat Khana would announce the arrival of the emperor and other dignitaries at the court of public audience (Diwan-i-Am). In addition to it, music was also played five times a day at chosen hours. It had been a tradition among the royal palaces  to have drum house at the entrance  that was meant to entertain the other royal dignitaries and rulers. Hathiyan pol or "elephant gate is yet another popular name for this structure because, in those days, the tradition was that every one but for people with royal blood would dismount from their elephant at this point. Beyond this point only royal members were allowed to ride the jumbo. 

This historical rectangular structure has three stories with the main band gallery measuring 100 feet x 80 feet. The primary construction material is red sandstone which is available near-by and the outer wall plastering is done in Chunam (ground lime for extra strength). The interior walls are well decorated and so are the exterior walls that have characteristic floral designs, which, it is mentioned, were  painted with gold.  Presently, the  first and second floors  consist of Indian War Memorial  museum.
Naqqar Khana near Fatehpur Sikri, Delhi  wikimedia.org

Taj, Agra, Naubat Khana. alamy.com
 This monument is being maintained by the Archaeological Survey of India. Like this Naubat Khana, The Taj Mahal complex has a Naqqar Khana as well.