…to the extent that an idea replaces another, I never cease to pass from one degree of perfection to another, however miniscule the difference, and this kind of melodic line of continuous variation will define affect (affectus) in its correlation with ideas and at the same time in its difference in nature from ideas. We account for this difference in nature and this correlation. It's up to you to say whether it agrees with you or not. We have got an entirely more solid definition of affectus; affectus in Spinoza is variation (he is speaking through my mouth; he didn't say it this way because he died too young...), continuous variation of the force of existing, insofar as this variation is determined by the ideas one has.
Deleuze, Lecture Notes on Spinoza
Deleuze’s analogy quoted above, presumes a harmonically varied composition of sounds following each other. This is probably, as Baker argues, based on Spinoza’s determinist philosophy which assumes a pre-established divine harmony that reminds one of Baroque applications of “contrapuntal writing, instrumental singularity, formal integrity, dialectical variation and harmonic structure”
[1] Ulus Baker, in his article “Bach and Spinoza” points out that Deleuze finishes his
Expressionism in Philosophy: Spinoza with a chapter named “Is Spinoza Baroque?”, and argues that “in the era of Bach, music is a world of pure affects.”
[2][3] And goes on to say that Third Part of Spinoza’s
Ethica might be read as a composition of affects.
However, with respect to the analogy of sound suggested by Deleuze, whether the sounds in the system follow each other harmonically is a matter of question. What is already determined is the variety of affection that a human being can experience; sadness and joy if Spinoza’s definition is followed, which corresponds to the limits of the human perception of sound which is almost between 20Hz to 200Khz. Since the external stimuli that effects us through affection ideas are mostly random, what we experience in our everyday lives within the limits of joy and sadness are not necessarily harmonical, on the contrary, they are more like continuous free flow of sound frequencies, rather than a Baroque piece.
However, we also have to keep in mind that mostly in our daily lives we are not totally conscious of or pay attention to this internal flow of power of existence just like we do not pay attention to the sounds we hear. How am I feeling at the moment or to which direction my feelings are changing to, are questions that would necessitate concentration to the psyche which would prevent one from concentrating on the routines and requirements of everyday life. However, there are times when we are alerted due to the strong impact that some experiences in variation. We mark those moments as privileged moments consciously or unconsciously and record them in our memory for a later recall.
Thus, the degree and character of affection that occurs in us when we encounter an image or an art work depicting a moment is very much related to our past experiences and set of mind at the time of encounter. When we are effected from an artwork an ordinary instant suddenly becomes a “privileged instant”; according to the strength of the "variation" it creates in us. The peak of the variation, either as a decrease or increase in our "power of existence" might be the reason why we want to look at the image which depicts a specific moment.
[1] Later, in the same article Baker argues that history of “Western Philosopy” and “Western music” can be read as a history of delays and even detentions. He suggests that Spinoza with its determinism delayed the “irrational” three hundred years until Nietzsche’s discovery of it as “life”. Similarly, Western music he argues delayed the dissonance until Schoenberg and had to discover the sound.
[2] http://www.korotonomedya.net/kor/index.php?id=8,112,0,0,1,0
[3] Baker states that “what would happen if Spinoza and Bach have met” was a question already asked before him by the Dutch philosopher Rabbi de Cardozo.