Sanchi Stupa
Bernard Gagnon, CC BY-SA 3.0 , via Wikimedia Commons

The first civilization to develop in India was built around the Indus River Valley. From 3500 - 1500 BC, it may have been one of the most densely populated parts of the world. The ruins of hundreds of cities have been discovered, the most famous being Mohenjo-daro and Harappa. These cities were centrally planned with multi-story buildings and advanced sanitation including sewage systems and public baths. There is very little evidence of war and few weapons have been discovered. Unfortunately, the Indus Script has never been deciphered, and the Indus Valley Civilization remains a significant mystery to historians.

A massive population influx of Indo-Aryans from Central Asia around 1750-1500 BC inaugurated the "Vedic Period," named after the sacred texts of Hinduism (the Rigveda, Yajurveda, Samaveda, and Atharvaveda), which developed during this time. The Vedas are written in Sanskrit, and considered to be of divine origin. The early Vedic civilization was socially structured into a caste system, with four stratified social groups or "varnas:"

• Brahmins (priests)
• Kshatriyas (rulers and warriors)
• Vaishyas (crafters and farmers)
• Shudras (workers)

This system remained more or less in place until the twentieth century.

The caste system created a very stable society, as it encouraged people to engage in svadharma-anushthana, fulfilling the duties of their caste, thereby gathering enough karma for their soul to earn a better place in future lives, and eventually be freed from saṃsāra, the cycle of reincarnation. Out of Hinduism rose many prominent world religions. The most significant are Jainism (9th to 5th century BC), Buddhism (6th century BC), and Sikhism (15th century AD). Of these, the most influential is Buddhism. Founded by a Hindu prince named Siddhartha Gautama, its philosophy is laid out by the Four Noble Truths and Noble Eightfold Path:

Indian music is a unique and richly traditional practice. Commonly, a tambura or similar instrument will sustain a tone while other instruments, such as the bansuri flute or multi-stringed sitar will float on top. Improvisation is common using a raga, one of various types of scale. The rhythm of Indian music is based on a tala, which roughly corresponds to a time signature, although is often quite complex.

Chandragupta Maurya united most of India under the Maurya Empire in 322 BC. The empire continued to expand under his son Bindusara and grandson Aśoka, eventually extending from Bangladesh in the east to Afghanistan in the west. Aśoka, however, after witnessing the brutality of his own troops in conquering Kalinga (in eastern India), converted to Buddhism and ended the conquests. After this, the empire declined until it was replaced in a coup by the Shunga Dynasty.

Some time during this period, a treatise on art, music, and dance called the Natyashastra was written, attributed to the sage Bharata Muni. Its twenty-eighth chapter identifies four groups of instruments, as in this 1951 translation by Dr. Manomohan Ghosh:

In 1914, two German ethnomusicologists named Curt Sachs and Erich Mortiz von Hornbostel devised a system for classifying instruments, called (naturally enough) the Sachs-Hornbostel Classification System. Instruments are identified by the method by which they produce sound: chordophones use vibrating strings; membranophones feature a membrane (drumhead) stretched to produce tension; ideophones, in which the instrument itself vibrates; and aerophones, which use a column of air blown through the instrument. Although the Sachs-Hornbostel system remains the most common terminology for classifying instruments, an ancient Sanskrit text had beaten them to the punch by nearly two millennia.

The Shunga dynasty collapsed during the first century BC. India was soon split between the Kushan Empire in the north and the Satavahana Dynasty on the subcontinent. As the influence of these empires waned in turn, many smaller kingdoms emerged, until most of India was again united in the Gupta Empire in 319 AD. The Ramayana by Valmiki and the Mahabharata by Vyasa, which is the longest of the ancient epic poems, reached their final form during this period. The Gupta Empire fell in 543 AD.