The Oxford Companion to Music defines music criticism as "the intellectual activity of formulating judgments on the value and degree of excellence of individual works of music, or whole groups or genres". In this sense, it is a branch of musical aesthetics.

With the concurrent expansion of interest in music and information media since the turn of the 20th century, the term has come to acquire the conventional meaning of journalistic reporting on musical performances.

The musicologist Winton Dean has suggested that "music is probably the most difficult of the arts to criticise." Unlike the plastic or literary arts, the 'language' of music does not specifically relate to human sensory experience – Dean's words, "the word 'love' is common coin in life and literature: the note C has nothing to do with breakfast or railway journeys or marital harmony." Like dramatic art, music is recreated at every performance, and criticism may, therefore, be directed both at the text (musical score) and the performance. More specifically, as music has a temporal dimension that requires repetition or development of its material "problems of balance, contrast, expectation and fulfilment... are more central to music than to other arts, supported as these are by verbal or representational content." The absence of a systematic or consensus-based musical aesthetics has also tended to make music criticism a highly subjective issue. "There is no counter-check outside the critic's own personality."

Critical references to music (often deprecating performers or styles) can be found in early literature, including, for example, in Plato's Laws and in the writings of medieval music theorists.

According to Richard Taruskin, the active concert life of late 18th-century London meant that "the role and the function of arts criticism as we know it today were the creations of the English public." However, the first magazines specifically devoted to music criticism seem to have developed in Germany, for example, Georg Philipp Telemann's Der getreue Music-Meister (1728), which included publications of new compositions, and Der kritische Musikus which appeared in Hamburg between 1737 and 1740. In France in the 1750s, the Querelle des Bouffons (the dispute between supporters of French and Italian opera styles as represented by Jean-Philippe Rameau and Jean-Baptiste Lully respectively) generated essays from Jean-Jacques Rousseau and others, including Denis Diderot's Rameau's Nephew (1761).

The English composer Charles Avison (1709–1770) published the first work on musical criticism in the English language – an Essay on Musical Expression published in 1752. In it, Avison claims that since the time of Palestrina and Raphael, music had improved in status whilst pictorial art had declined. However, he believes that George Frideric Handel is too much concerned with naturalistic imitation than with expression, and criticises the habit, in Italian operas, of

that egregious absurdity of repeating, and finishing many songs with the first part; when it often happens, after the passions of anger and revenge have been sufficiently expressed, that reconcilement and love are the subjects of the second, and, therefore, should conclude the performance.

Typically, until the late eighteenth century, music criticism centred on vocal rather than instrumental music – "vocal music ... was the apex of [the] aesthetic hierarchy. One knew what music was expressing."