Throughout the second half of the 20th century, Gustav Leonhardt, who has died aged 83, was a pioneer and pillar of the early music movement. As a harpsichordist, organist, scholar, conductor and teacher, he was a major figure, exercising very considerable influence on his contemporaries and juniors, and in particular making the Netherlands a focal centre for the performance of Baroque music, gathering round himself artists such as the recorder virtuoso Frans Brüggen, the viola da gamba player and cellist Anner Bylsma, the cellist and conductor Nikolaus Harnoncourt and the Kuijken brothers – Barthold, Sigiswald and Wieland – all now pre-eminent in their fields.
Himself an intensely serious-minded musician, Leonhardt sought to present 17th- and 18th-century music on period instruments or copies thereof, and in accordance with the performance practice of those times, without concessions to later tastes – though he once said (perhaps somewhat questionably): "If one manages to be convincing, the interpretation sounds authentic: if one strives to be authentic, one will never be convincing."
His own playing was marked by superlative technical assurance, lucidity, intellectual authority and gravitas – gaiety and humour came less easily to him – and initially he was criticised for too coolly dispassionate and austere a style: later, however, he himself acknowledged that he might have been over-severe and adopted a more relaxed, more expressive approach.
Many of today's leading harpsichordists were pupils of his, which sometimes led to awkward situations when he was on the jury of international competitions. One particular area in which he made a valuable contribution was the series of records of all Bach's cantatas that he and Harnoncourt conducted between 1972 and 1990 – a vast intégrale only later copied by others.
Leonhardt was born in 's-Graveland, near Hilversum. During the German occupation of the Netherlands in the second world war, he was unable to leave the house for nine months, sleeping on boards between the floors and with someone always on lookout. At the age of 18, after a brief classical education, he entered the Schola Cantorum Basiliensis, in Switzerland, whose director was the conductor and musical patron Paul Sacher, to study organ and harpsichord with Eduard Müller and ensemble playing with August Wenzinger: three years later he went to Vienna to study conducting with Hans Swarowsky.
In 1950 he made his debut in Vienna playing Bach's Art of Fugue, which he stoutly maintained had been intended for the harpsichord, but of which the final incomplete fugue did not form part: he wrote a monograph on the subject and, 30 years later, recorded the work. He rapidly made a name as a harpsichordist, at the age of 24 became professor of the instrument at the Vienna Academy of Music, and the following year at the Amsterdam Conservatoire. There he settled permanently and was appointed organist at the Waalse Kerk, which boasted a splendid organ of 1733.
Around this time he started making his numerous recordings – a concerto by Johann Christian Bach under Sacher, the first of what would eventually be three recordings of Bach's Goldberg Variations – and, with a small ensemble, discs with the English contertenor Alfred Deller, from whom he declared he learned much about nuance and phrasing. He also formed the Leonhardt Consort, which, for 20 years, made historical instruments the norm for this period of the repertoire to such an extent that he later declared: "If you hear a modern violin, you are almost startled."