  A prominent theory of affective response to music revolves around the
concepts of surprisal and expectation. In prior work, this idea has been
operationalized in the form of probabilistic models of music which allow for
precise computation of song (or note-by-note) probabilities, conditioned on a
'training set' of prior musical or cultural experiences. To date, however,
these models have been limited to compute exact probabilities through
hand-crafted features or restricted to linear models which are likely not
sufficient to represent the complex conditional distributions present in music.
In this work, we propose to use modern deep probabilistic generative models in
the form of a Diffusion Model to compute an approximate likelihood of a musical
input sequence. Unlike prior work, such a generative model parameterized by
deep neural networks is able to learn complex non-linear features directly from
a training set itself. In doing so, we expect to find that such models are able
to more accurately represent the 'surprisal' of music for human listeners. From
the literature, it is known that there is an inverted U-shaped relationship
between surprisal and the amount human subjects 'like' a given song. In this
work we show that pre-trained diffusion models indeed yield musical surprisal
values which exhibit a negative quadratic relationship with measured subject
'liking' ratings, and that the quality of this relationship is competitive with
state of the art methods such as IDyOM. We therefore present this model a
preliminary step in developing modern deep generative models of music
expectation and subjective likability.
