1784 in music
- January 5 - In Paris, Antonio Salieri signs a contract with the Opéra for a work entitled Les Danaïdes.
- January 7 - Composer Pierre-Alexandre Monsigny marries Amélie de Villemagne.
- February 9 - The Piano Concerto No. 14 becomes the first entry in the catalogue of works by Wolfgang Amadeus Mozart.
- March - 28-year-old Mozart gives the first performances of his Piano Concerto No. 15 at the Trattnerhof and Burgtheater in Vienna.
- April 24 - Mozart writes to his father Leopold, recommending the work of newcomer Ignaz Pleyel.
- April 29 – Wolfgang Amadeus Mozart and violinist Regina Strinasacchi perform Mozart's Sonata in B flat for Violin and Keyboard (K.454) for the first time, in the presence of Joseph II, Holy Roman Emperor.
- May 8 - Pasquale Anfossi's drama with music, Issipile, based on words by Metastasio, receives its première at the King's Theatre, London.
- June 13 - Wolfgang Amadeus Mozart's Piano Concerto No. 17 is performed for the first time, by his student, Barbara von Ployer. Giovanni Paisiello is in the audience.
- July 10 - Domenico Cimarosa's drama with music, L’Olimpiade, based on words by Metastasio, receives its première at the Teatro Eretenio, Vicenza.
- August 17 - Luigi Boccherini is given a pay rise of 12000 reals by his employer, the Infante Luis, Count of Chinchón.
- August 28 - In Vienna, Johann Georg Albrechtsberger's Mass in E flat is performed for the first time, with the orchestral arrangement replaced by organ accompaniment, in accordance with the preferences of Joseph II, Holy Roman Emperor.
- December 11 - Mozart is received into the Masonic lodge "Beneficence".
- The first opera is mounted at the unfinished Teatro Nuovo in Bergamo, Lombardy, Giuseppe Sarti's Medonte, re di Epiro.
- Michael Haydn – Symphony in B flat major; Symphony in C major
- Wolfgang Amadeus Mozart
- Piano Concerto No. 14
- Piano Concerto No. 15
- Giovanni Battista Viotti – Duetto concertante for 2 Violins in D major; Duetto concertante for 2 Violins in D minor
- Luigi Cherubini - L'Idalide
- André Grétry – Richard Coeur de Lion
- Joseph Haydn – Armida
- Thomas Linley – The Spanish Rivals
- Antonio Salieri
- Andrea Luchesi – Ademira
- Giovanni Paisiello – Il Re Teodoro
- Niccolò Piccinni - Diane et Endymion
- January 1 – William Beale, composer and organist (died 1854)
- January 27 – Martin-Joseph Mengal, composer (died 1851)
- January 29 – Ferdinand Ries, composer
- February 3 – John Fane, composer and diplomat
- February 27 – Job Plimpton, composer (died 1864)
- March 25 - François-Joseph Fétis, Belgian musicologist, composer, critic and teacher (died 1871)
- April 8 – Dionisio Aguado, guitarist and composer (died 1849)
- June 14 - Francesco Morlacchi, opera composer (died 1841)
- July 27 – George Onslow, composer (died 1853)
- August 5 – Louis Spohr, composer, violinist and conductor (died 1859)
- August 23
- October 15 – Thomas Hastings, composer (died 1872)
- November 7 – Friedrich Wilhelm Kalkbrenner, German pianist and composer
- date unknown - Samuel Simms, organist and composer (died 1868)
- March 4 – Ann Cargill, opera singer (born 1760) (drowned)
- July 1 – Wilhelm Friedemann Bach, composer (born 1710)
- August – Louis Anseaume, opera librettist
- August 6 – Karl Kohaut, lutenist and composer (born 1726)
- August 4 – Giovanni Battista Martini, composer (born 1706)
- September 12 – Manuel Blasco de Nebra, organist and composer (born 1750)
- October 5 (or 1785) - Antonín Kammel, violinist and composer (born 1730)
- November 6 - Anine Frölich, ballet dancer (born 1762)
- date unknown
- MusicAndHistory:1764 Accessed 21 April 2013