Steve Reich is not yet 90, but the celebrations have already begun. His new piece for large ensemble, In All Your Ways, received its world premiere at the Edinburgh festival last month, followed by a late-night concert at the BBC Proms.

The composer reaches his ninth decade on 3 October. Asked how he feels about becoming a nonagenarian, Reich is coy. "I haven't quite got there yet," he says. "I don't want to dot the i before I even get there. I'll let you know in due course …"

Reich's path began early. At 14, he heard Stravinsky and resolved to become a composer. Born in New York in 1936, he has spent the last six decades producing music that has changed the soundtrack of modern life in Europe and North America.

The scale of his influence is hard to overstate. He is revered by figures such as David Bowie, and music critics have lavished superlatives on his work. The New Yorker has called him "the most original musical thinker of our time".

Alongside contemporaries such as Philip Glass, Reich built the minimalist movement from its foundations, and its techniques — repetition, phasing, steady pulse — have since seeped into contemporary classical music, rock, electronic dance music and film scores. His ideas about rhythm and structure reshaped how composers on both sides of the Atlantic approached the orchestra and the ensemble.

Yet Reich himself is unsentimental about musical quality. "Good music is good music, and most music is not!" he declared — a blunt credo from a composer who has never softened his judgments about the art form he has shaped for 60 years.

The birthday programming tells its own story. In All Your Ways, scored for large ensemble, marks one of the most substantial additions to his catalogue in recent years, and its premiere at Edinburgh placed Reich at the centre of one of Europe's major summer festivals. The subsequent Proms appearance gave London audiences their own salute.

With the 3 October milestone still ahead of him, Reich is keeping his reflections short. "I'll let you know in due course," he says. Audiences, ensembles and festival programmers worldwide will be listening for what comes next — from a composer who, even at 90, has not finished having the last word.