Realistically a number of ancient Indian mural paintings, sculptures, literal and ancient theoretical works hold reference of the presence of the four primordial instruments like the Veena, Venu Mridanga and Damaru. With the passage of time, these Indian musical instruments underwent a thousand transformation and mutations and diversified into numerous other instruments. Regional as well as the geographical factors indeed contributed to the diversity of the tonal quality and in the variations in the designs of the Indian musical instruments. Many of the musical instruments seen today evolved in the medieval India owing to contacts with the Persian and Middle Eastern cultures. A number of musical instruments germinated as a result of the cultural fusion with the Islamic invasion in India. Rubab is one such musical instrument which came to India from Persia via Afghanistan during the time of early Islamic invasion and was indeed a part of the musical ensemble of the Mughal era.
With the advent of the colonial era, Indian musical instruments underwent a sea change. Instruments like the violin, the guitar, the mandolin, the clarinet and the saxophone were imported from the West and were largely absorbed in the philosophy of Indian music.
Whatever be the origin, however deep may be the influence of society, culture, more and tradition in delineating the tone, form and designs of Indian musical instruments, in broader aspect Indian musical instruments can be classified into four main heads depending upon the sound they produce. Bharata muni in his Natyashastra also classified Indian musical instruments into four broad categories namely, the stringed instruments (tat or Tantra Vadya), the wind instruments (Sushira Vadya), the Ghana Vadya and the percussion instruments (Avanaddha Vadya). This mode of classification even survives today despite the introduction of newer musical instruments into the field.
The string instruments are those which produce sounds when the strings are plucked with a finger or strapped, slapped or strummed. Indian musical instruments like the Rudra Veena, sitar, sarod and even Surbahar fall in this category. There is another category of stringed instrument like the violin, esraj, dilruba and the tar Shehnai, which make use of a bow to produce an uninterrupted series of notes.
Wind instruments on the other hand produce music when an unbroken stream of air is blown through them. The wind instruments like the flute, shehnai and the clarinet generate a sound when a column of air is made to vibrate inside them. The frequency of the wave generated is related to the length of the column of air and the shape of the instrument, while the tone quality of the sound generated is affected by the construction of the instrument and method of tone production.
The Ghana Vadya is the Indian musical instruments which produce music when the strings are struck with strikers made of wood or metal. Instruments like santoor, jaltarang falls in this category. The percussion instruments amongst wide variety of the Indian musical instruments are the ones which create sound with or without pitch when drummed. The North Indian Pakhvaj, the South Indian Mridanga, Dholak and tabla are the percussion instruments which are made of animal membranes and produce sound if and when drummed.
Indian musical instruments since ages with their timbre, style and form has silhouetted the Indian music to a great extent. The legacy of Indian musical instrument which started by the divinities and sub divinities by the musical orchestra in manning the "terrible sublime sound" of the Damaru of Lord Shiva is no more just a mythological concept but a concrete realism in shaping the musical tradition in India.