JOHN W. DUARTE was one of the most prolific 20th-century composers for the guitar, but he was also an author, a music critic and a teacher. He instructed at summer schools, festivals and conservatories worldwide, as well as writing for all the major international guitar journals and many important music publications, including the New Grove Dictionary of Music and Musicians.

His energy for creative activities and endless globetrotting remained seemingly inexhaustible right up to the last year of his life. Wherever in the world the leading classical guitarists and their students gathered, Duarte was a familiar presence.

Duarte published more than 200 original works and arrangements, and his music was recorded by such recitalists as Andrés Segovia and John Williams. From the 1940s, he became a powerful and uncompromising writer on the classical guitar, establishing a new and vital critique of the instrument and its players in articles and correspondence columns.

Greatly in demand as a teacher of the guitar both privately and at international summer schools, Duarte always acknowledged that in the pedagogic field he was something of an anomaly, never having undertaken a formal academic training in music nor possessing any aspirations of becoming a concert player.

Nonetheless, through close observation of many leading guitarists, Duarte acquired a unique insight into the essentials of both technique and interpretation. Thus he once described himself as “one who does not pretend to any status as a performer . . . a mere observer whose findings have been confirmed by sufficient virtuosi to set my conscience at rest”.

John William Duarte was born in Sheffield, but lived in Manchester from the age of 6. After hearing a banjo and becoming fascinated by fretted instruments, he acquired his first guitar (at the cost of £1) in 1934. Initially he studied jazz guitar with the Manchester guitarist Terry Usher, though with no intention of becoming a professional musician.

Instead, Duarte graduated in chemistry at Manchester University, where during his student years he learnt trumpet and double bass (playing the latter on occasion in the company of Coleman Hawkins and Django Reinhardt).

During the war he was employed as chief chemist in a Ministry of Supply factory. When the war ended, Duarte, a founder member of the Manchester Guitar Circle, was first introduced to Andrés Segovia, who became a lifelong friend.

From the 1950s Duarte concentrated on the classical guitar, moving to London (though still working as an industrial chemist) to teach at the Spanish Guitar Centre. There, he increased his composing activities and establish creative links with a number of great players. He steadily built up a formidable international reputation and in 1973 he became a full-time composer, critic and teacher.

In 1977 Duarte was appointed director of the Cannington Summer School, which attracted students from all over the world, and he continued there until the 1990s.

From 1978 until just a few months ago, he wrote regularly for Gramophone magazine, where his brief soon developed to cover not only the guitar but also the harpsichord, Baroque music and interviews with distinguished performers.

Over the years his musical output proliferated until his works had been recorded by some 60 artists in more than 20 countries. His critical writing, a substantial contribution to British musical life, included about 250 compact disc liner notes, with a Grammy Award for his annotation to the reissue of Segovia’s early recordings. He became a familiar figure on international juries for guitar competitions and taught in more than 30 countries.

His 60th, 70th and 80th birthdays were celebrated by Wigmore Hall and Bolivar Hall recitals of his music, performed by artists from many countries. In 1990 he was presented with a Silver Medal by the Czech Ambassador for services to Anglo-Czech and Slovak cultural relations, and in 1999 he was honoured with the Award for Lifetime Achievement from the Guitar Foundation of America.

In 2001 the notes of a Naxos recording of Duarte’s music provided his compositional credo: “As a composer I have never given much thought to what posterity might think of me — I will not be here to know it! My aim is to write primarily for the living and hopefully to give pleasure.”

He is survived by his wife, Dorothy, whom he married in 1943, and by two sons and a daughter.

John W. Duarte, composer, writer and teacher, was born on October 2, 1919. He died on December 23, 2004, aged 85.