The term "classical music" has two meanings: the broader meaning includes all Western art music from the Medieval era to the 2000s, and the specific meaning refers to the art music from the 1750s to the early 1820s—the period of Wolfgang Amadeus Mozart, Joseph Haydn, and Ludwig van Beethoven. This section is about the more specific meaning. Classical era musicians continued to use many of instruments from the Baroque era, such as the cello, contrabass, recorder, trombone, timpani, fortepiano (the precursor to the modern piano) and organ. While some Baroque instruments fell into disuse (e.g., the theorbo and rackett), many Baroque instruments were changed into the versions that are still in use today, such as the Baroque violin (which became the violin), the Baroque oboe (which became the oboe) and the Baroque trumpet, which transitioned to the regular valved trumpet.

During the Classical era, the stringed instruments used in orchestra and chamber music such as string quartets were standardized as the four instruments which form the string section of the orchestra: the violin, viola, cello and double bass. Baroque-era stringed instruments such as fretted, bowed viols were phased out. Woodwinds included the basset clarinet, basset horn, clarinette d'amour, the Classical clarinet, the chalumeau, the flute, oboe and bassoon. Keyboard instruments included the clavichord and the fortepiano. While the harpsichord was still used in basso continuo accompaniment in the 1750s and 1760s, it fell out of use in the end of the century. Brass instruments included the buccin, the ophicleide (a replacement for the bass serpent, which was the precursor of the tuba) and the natural horn.

Almost all of the composers who are described in music textbooks on classical music and whose works are widely performed as part of the standard concert repertoire are male composers, even though there has been a large number of women composers throughout the classical music period. Musicologist Marcia Citron has asked "[w]hy is music composed by women so marginal to the standard 'classical' repertoire?"[64] Citron "examines the practices and attitudes that have led to the exclusion of women composers from the received 'canon' of performed musical works."

She argues that in the 1800s, women composers typically wrote art songs for performance in small recitals rather than symphonies intended for performance with an orchestra in a large hall, with the latter works being seen as the most important genre for composers; since women composers did not write many symphonies, they were deemed to be not notable as composers.[64] In the "...Concise Oxford History of Music, Clara S[c]humann is one of the only [sic] female composers mentioned."[65] Abbey Philips states that "[d]uring the 20th century the women who were composing/playing gained far less attention than their male counterparts.