Glass had still not found his style when, in the 1960s, he went to study under Nadia Boulanger in Paris. There he transcribed into Western notation the Indian music of the famous sitarist Ravi Shankar, and his discovery of Oriental musical techniques had a profound effect on his own work. He went on to research music in North Africa and India, and began to develop his own distinctive style. His work was also strongly influenced by other American minimalists, such as Steve Reich and Terry Riley.

In 1967, Glass returned to New York, where he slowly assembled a group of musicians to play his innovatory music. Using woodwinds, keyboards and amplified voices, this group was an early version of what came to be known as the Philip Glass Ensemble. The works consisted of syncopated rhythms that contracted or expanded within a stable structure, producing a whirl of hypnotic musical patterns that fascinated some listeners but seemed like mindless repetition to others.

Gradually, however, Glass built up a following, and his opera Einstein on the Beach (1976), in collaboration with Robert Wilson, attained cult status in the international musical community. It was followed by Satyagraha (1980), an opera about the life of Gandhi the saintly Indian advocate of non-violent resistance (satyagraha). With a libretto using the Bhagavadgita Hindu scripture, the opera built up a mesmeric power with its series of symmetrical chord sequences. In 1992, Glass produced, on commission from the New York Metropolitan Opera, The Voyage, an opera to commemorate Columbus' arrival in the Americas.

More recently, Glass has written the Heroes Symphony for American choreographer Twyla Tharp, for which he used themes from popular musicians David Bowie and Brian Eno. He has also written the score for Martin Scorsese's film about the Dalai Lama, Kundun (1998), for which Glass received a Golden Globe nomination and an Academy Award nomination for best score.