Perhaps influenced by Antonello da Messina's introduction of the Early Netherlandish style of portrait painting to Italy, the work marks a dramatic shift from the profile portraiture that predominated in 15th-century Milan.

Other notable suggestions include Josquin des Prez and Gaspar van Weerbeke, but there is no historical evidence to substantiate any of these claims.

[4] It depicts a young man in bust length and three-quarter view, whose right hand holds a folded piece of sheet music.

[5][6] The painting is largely unfinished save for the face and hair,[4] but is in good condition overall, with only the bottom right corner suffering damage.

[2][7] The art historian Kenneth Clark noted that out of Leonardo's surviving works, the Musician is perhaps the best preserved,[8] despite the fading of colors over time.

[18][19] Some have argued that this is simply for dramatic effect, so that the viewer feels a sense of motion from the musician's left to right side of his face.

[19] The art historian Luke Syson has written that "the eyes are perhaps the most striking feature of the Musician, sight given primacy as the noblest sense and the most important tool of the painter".

[20] The partially erased letters can be made out as "Cant" and "An"[21] and are usually read as "Cantum Angelicum", Latin for 'angelic song', although the art historian Martin Kemp notes that it could be "Cantore Angelico", Italian for 'angelic singer'.

[5] Although the attribution to Leonardo had been controversial in earlier centuries, modern art historians now regard the Portrait of a Musician as one of his original works.

[4] When first listed in 1672, it was described as having "all the elegance that might be expected of a ducal commission",[4][n 3] which implies that the subject was thought to be Ludovico Sforza, Duke of Milan, who was Leonardo's employer when the painting was executed.

[12] Its attribution to Leonardo is based on stylistic and technical similarities to other works by him,[8] notably the face of the angel in the Louvre Virgin of the Rocks[2] and that of the titular figure in Saint Jerome in the Wilderness.

[15][n 5] The dark background of the portrait, a style popularized by Leonardo, furthers this attribution as it appears in later paintings by him, such as the Lady with an Ermine, La Belle Ferronnière and Saint John the Baptist.

[7] Other characteristics typical of Leonardo's style include the melancholic atmosphere, the sensitive eyes,[2] the ambiguous mouth (which seems to have just closed or is about to open), and curly hair[4] reminiscent of his earlier portrait, Ginevra de' Benci.

[7] If Leonardo was assisted by another artist, the most frequently cited candidates are Boltraffio and Ambrogio de Predis,[4] due to their style being closer to the hard and rigid qualities of the portrait.

[21][28] Modern scholars, including Syson and Marani, have observed that Leonardo could not have executed the portrait much later than 1487,[22][26] as it is considered to lack the refinement and realism of later works informed by his anatomical studies, such as the Lady with an Ermine.

[29] The Milanese audience was more artistically conservative than others elsewhere in Italy,[30] and would have expected most, if not all, portraits to be in profile, like those by Zanetto Bugatto, Vincenzo Foppa and Ambrogio Bergognone.

[29] The sitter's three-quarter profile was already common in Early Netherlandish painting, where portraits were often set against a flat black background.

[29] It is generally thought not to have been among the works gifted to the Ambrosiana by its founder, Cardinal Federico Borromeo, in 1618,[25] which at the time made up the bulk of the museum's collection.

[41] The identification of the sitter as Ludovico was accepted until a 1904–1905 restoration by Luigi Cavenaghi and Antonio Grandi removed a layer of overpaint and revealed a hand holding sheet music.

[5][17][18] In 1972 the Belgian musicologist Suzanne Clercx-Lejeune [fr] proposed the French singer and composer Josquin des Prez (c. 1450–55 – 1521) as the sitter.

[43] At the end of the 19th century, the subject of the portrait was identified by Paul Müller-Walde [de] as Galeazzo Sanseverino, Ludovico's son-in-law and captain general of the Sforza militias, a prominent figure of the Milanese court.

[49] In support of this thesis, the Italian scholar Piero Misciatelli recalls that Galeazzo had been a patron of Leonardo and was probably passionate about music.

[50] Other scholars, such as the French art historian Robert de la Sizeranne [fr], have recognized the traits of his father, Roberto Sanseverino.

[51][52] Gian Galeazzo Sforza (1469–1494) has been proposed, given that the original, vague, description of the portrait stated that it depicted the Duke of Milan.

[16] Francesco Canova da Milano (1497–1543), an Italian lutenist and composer,[53] and the Flemish singer Giovanni Cordier have been proposed, albeit without substantive evidence.

[54] The critical opinion of the Portrait of a Musician has historically been mixed, and negative reactions have given some scholars reluctance to grant it a full attribution to Leonardo.

[4] The 19th-century art historian Eugène Müntz complemented its "vigor of modeling worthy of Rembrandt", but criticized the work for a sullen expression, poor coloring and incompleteness.

[56] Like Müntz, Zöllner found fault with the work's incompleteness and expression; he also considered its pose inferior to that of Ginevra de' Benci.

Music is to be regarded none other than the sister of painting since it is subject to hearing, a sense second to the eye, and since it composes harmony from the conjunction of its proportional parts operating at the same time.