Evert Cornelis was a Dutch conductor and organist. He was born in Amsterdam on 5 December 1884, the son of lithographer Arnold George Cornelis and Evertje Oostervink. Although he grew up in a Reformed household with little interest in music, his talent became apparent early.
Supported by Daniël de Lange, Cornelis received a scholarship to attend music school and entered the Amsterdam Conservatory at the age of 15, studying there from 1898 to 1904. He studied organ and piano with Jean-Baptiste de Pauw and composition with Bernard Zweers. After winning the Prix d'Excellence for organ in 1904, he became organist in Ouderkerk aan de Amstel and subsequently served at Amsterdam's Old Lutheran Church until 1923. He was known for his varied repertoire and advocated the music of Max Reger at a time when it was considered difficult.
His main interest was conducting. In 1904 he became répétiteur at the Royal Flemish Opera in Antwerp and later assistant conductor at the briefly revived Dutch Opera led by Cornelis van der Linden. In 1907 he accompanied soprano Alida Loman-Lütkemann on a tour of the Dutch East Indies and Australia.
After unsuccessfully asking Willem Mengelberg for a position as second conductor of the Concertgebouw Orchestra in 1908, Cornelis was invited to take the post in 1909. Though initially subordinate, he became increasingly indispensable to the orchestra. He broadened its repertoire with contemporary classical music and early music, areas that interested Mengelberg and fellow second conductor Cornelis Dopper less, and he also favoured the music of Claude Debussy and Maurice Ravel.
After leaving the Concertgebouw Orchestra, Cornelis concentrated for several years on solo performance, chamber music, choral conducting, and accompanying the Belgian soprano Berthe Seroen. They worked together for fourteen years. Their Seroen-Cornelis recital evenings successfully introduced songs by French composers including Ernest Chausson, Henri Duparc, Gabriel Fauré, Debussy, and Ravel.
In 1922 Cornelis became principal conductor of the Utrecht Municipal Orchestra. He restored the ensemble after a difficult period and developed ambitious, carefully planned programmes, supported by detailed programme notes. He introduced much Dutch and international twentieth-century music, including works by Igor Stravinsky, Arthur Honegger, Béla Bartók, Zoltán Kodály, Arnold Schoenberg, and Anton Webern, while also programming music from other periods. He was one of the few conductors of his time to programme Anton Bruckner's symphonies, and critics particularly praised his interpretation of César Franck's Symphony in D minor. Charles Tournemire, whose music Cornelis championed, dedicated two works to him.
With the Utrecht Municipal Orchestra, Cornelis gave concert performances of complete operas, including Debussy's Pelléas et Mélisande, with Seroen as Mélisande. He also performed British music rarely heard in the Netherlands, including works by Frederick Delius and Ralph Vaughan Williams. A pioneer of historically informed Baroque performance, he used the harpsichord for basso continuo. From 1927, following the death of Johan Schoonderbeek, he also led the Netherlands Bach Society, becoming the first conductor to perform Bach's St Matthew Passion and St John Passion complete and without the customary cuts, and the first in the Netherlands to use Handel's English text for Messiah rather than the customary German version.
Cornelis married Hilda Whitley on 6 February 1908; they had a daughter and a son, Evert Cornelis Jr., who became a lawyer and later served as director and general manager of cultural institutions including the Residentie Orchestra, the Holland Festival, and the Dutch Opera. Despite poor health and an incurable illness, Cornelis remained an active musician and conducted a subscription concert after leaving his bed twelve days before his death. He died in Bilthoven on 23 November 1931, shortly before his forty-seventh birthday. A bronze bust by Gra Rueb was unveiled at Utrecht's Tivoli in 1956, and an oil portrait by Willem van Nieuwenhoven has hung in the Concertgebouw's conductors' foyer since 1954.