Conceive of a picture really as a series of harmonies.

Aesthetic:
Art is Harmony.
Harmony is the analogy of opposites, the analogy of similarities of tone, of tint, of line taking account of a dominant and under the influence of the lighting, in combinations that are gay calm or sad.

Why should not I call my works 'symphonies', 'arrangements', 'harmonies', and 'nocturnes'?.. .The vast majority of English folk cannot and will not consider a picture as a picture, apart from any story which it may be supposed to tell. My picture of 'Harmony in Grey and Gold' is an illustration of my meaning – as snow scene with a single black figure and lighted tavern. I care nothing for the past, present, or future of the black figure, placed there because the black was wanted at that spot. All that I know is that my combination of grey and gold is the basis of the picture, Now this is precisely what my friends cannot grasp.

I borrow some subject or other from life or from nature, and, using it as a pretext, I arrange lines and colors so as to obtain symphonies, harmonies that do not represent a thing that is real, in the vulgar sense of the word, and do not directly express any idea, but are supposed to make you think the way music is supposed to make you think, unaided by ideas or images, simply through the mysterious affinities that exist between our brains and such arrangements of colors and lines.

Great art should come from the harmony of two lines.

I can look a whole day with delight upon a handsome picture, though it be but of a horse. It is my temper, & I like it the better, to affect all harmony, and sure there is music even in the beauty, and the silent note which Cupid strikes, far sweeter than the sound of an instrument. For there is a music wherever there is a harmony, order or proportion; and thus far we may maintain the music of the spheres.

Beauty of style and harmony and grace and good rhythm depend on simplicity

Well! according to the sketch your picture [which Whistler sent him in a letter] seems well-composed, the lines of sky, sea, the position of the figures all that seems very, very well done[,] on opening the letter it struck me immediately, an impression of decorative ornamentation which makes a good picture appeal to the eye as well - upside down and any other way up. Arrangement, layout, composition. etc - mysterious words harmonious laws - in no way conventional - needs of the Artist glory of the Raphael's Michelangelo's etc etc - for me a repetition a hesitation, a matter of feeling - which should also be a law, a mathematical thing, like form, like light, colour[.] I find similarities with the colour method which works by opposing colours to arrive at a harmony that is to say to make a canvas a complete whole, to put into a small space an image with all the forces all the principles of nature - [instead of showing a part of it]..

There is a musicke where-ever there is a harmony, order or proportion; and thus farre we may maintain the musick of the spheares; for those well ordered motions, and regular paces, though they give no sound unto the era, yet to the understanding they strike a note most full of harmony. Whatever is harmonically composed delights in harmony; which makes me much distrust the symmetry of those heads which declaime against all Church musicke. For my self, not only from my obedience but my particular genius, I doe embrace it; for even that vulgar and Taverne Musicke, which makes one man merry, another mad, strikes in mee a deepe fit of devotion, and a profound contemplation of the first composer; there is something in it of Divinity more than the eare discovers. It is an Hieroglyphicall and shadowed lesson of the whole world, and Creatures of God, such a melody to the eare, as the whole world well understood, would afford the understanding. In briefe it is a sensible fit of that Harmony, which intellectually sounds in the eares of God.

There is a musicke where-ever there is a harmony, order or proportion; and thus farre we may maintain the musick of the spheares; for those well ordered motions, and regular paces, though they give no sound unto the eare, yet to the understanding they strike a note most full of harmony. Whatever is harmonically composed delights in harmony; which makes me much distrust the symmetry of those heads which declaime against all Church musicke. For my self, not only from my obedience but my particular genius, I doe embrace it; for even that vulgar and Taverne Musicke, which makes one man merry, another mad, strikes in mee a deepe fit of devotion, and a profound contemplation of the first composer; there is something in it of Divinity more than the eare discovers. It is an Hieroglyphicall and shadowed lesson of the whole world, and Creatures of God, such a melody to the eare, as the whole world well understood, would afford the understanding. In briefe it is a sensible fit of that Harmony, which intellectually sounds in the eares of God.

Harmony. ...it is all embracing and should reign throughout—harmony in purpose, harmony in dimensions, harmony in form and harmony in color. In good design discord can have no place. ...all may unite to form a complete, harmonious, and well-rounded composition ...

..colors are my notes for fashioning sounds and chords with and against one another.

The opposition between structure and sonority in music is almost as misleading as that between line and color in the visual arts. Baudelaire insisted, correctly, that Delacroix was one of the three greatest draftsmen of the century, and emphasized his mastery of line. In the same way, a study of Chopin demonstrates the intimate relation between line and color in music.

Melody is what makes a song a memory.