Ganga-Jamuni tehzeeb

Ganga–Jamuni Tehzeeb (Hindustani for "Ganges–Yamuna Culture"), also spelled as Ganga-Jamni Tehzeeb, is the culture of the central plains of northern India, especially the doab region of Ganges (Ganga) and Yamuna rivers, that is a syncretic fusion of Hindu cultural elements with Muslim religious elements.
K. Warikoo, Professor at the Centre for Inner Asian Studies at Jawaharlal Nehru University describes the concept as one exemplifying communal harmony and a shared culture between the Hindus and Muslims of India:
Ganga-Jamuni tehzeeb, a poetic Awadhi phrase for a distinctive and syncretic Hindu-Muslim culture, is reflected in the fused spiritual connotations, forms, symbols, aesthetics, crafts and weaves, for example Kashmiri Muslim carpet makers feature Durga in their patterns, Muslim sculptors making idols of Durga, and Hindu craftsmen create the Muharram tazia. This religious syncretism based on the vasudhaiva kutumbakam, unity in diversity and multi-communitarianism is a result of centuries of interfaith exchange and accommodation among Indian religions (Hinduism, Buddhism, Jainism, Sikhism) and foreign origin religions (Muslim and Christian) where in India communities preserve own cultural and religious identies while facilitating the shared celebration of festivals, customs and traditions. The shared Indian national identity is separated from the personal religious identity where nation and common social good comes first above the personal religion. 
Various iconic people of several religions related to the Bhakti movement, a medieval initiative for the revival and recontextualisation of ancient Vedic traditions, are example of this tehzeeb.
Etymology.
"Ganga-Jamni" Hindi, literally, "mixed," "composite," "alloy," "Tahzeeb", Urdu, via Arabic: تہذيب tahẕīb edification, refinement, polish, culture.
Revolutionary role of bhakti movement.
Surdas, Guru Nanak, Ravidas, Kabir, Bulleh Shah, Tulsidas, Gusainji, Ramananda, Eknath, Tukaram, Mirabai were some of the prominent contributors of bhakti movement. One of the best examples of syncretic faith is captured in one of Kabir's doha (verse), "some chant Allah, some chant Ram, Kabir is a worshiper of true love and hence reveres both."
Regional practices.
Awadh.
Nawabs of Awadh were fore-runners of this culture. The region of Awadh in the state of Uttar Pradesh is usually considered to be the center of this culture. Allahabad, Lucknow, Kanpur, Faizabad-Ayodhya, and Varanasi (Benares) are a few of the many centers of this culture.
Delhi.
Delhi has also historically been a prime example of the Ganga-Jamuna Tahzeeb; with its iconic Khariboli dialect and being one of the literally centers of the Urdu language, there have been numerous poets such as Amir Khusrow, Mir Taqi Mir, Ghalib, Mohammad Ibrahim Zauq, Daagh Dehlvi, Nida Fazli and many others. Delhi has also contributed to the music of the region, being the birthplace of Qawwali and the Delhi Gharana. Though, there has been conflict between Hindus and Muslims after 2020 Delhi riots.
Hyderabad.
Hyderabad, the capital city of Telangana in south-central part of the India, is also a big example of communal harmony where the local Telugu Hindus and Hyderabadi Muslims live with peace and brotherhood, where Hindu temples serve the dry dates fruits to mosques for Iftar Muslim festival.