Processing music: a Top-Down and Bottom-Up Approach

So you're listening to music. As I've mentioned before, all this means is that air molecules are vibrating in certain ways and beating against aural membrane in given patterns. But how do we make thoughtful sense of this physical phenomenon? Our brains, upon receiving musical input, extract it into features (pitch, rhythm etc.) and then integrate the features to form broader musical concepts.

So let's say the stimulus here is an outside source such as music playing from your headphones. Certain neural networks extract what you hear into features such as rhythm and pitch. This is called bottom-up processing: we are only concerned at this stage with what's coming directly from stimulus. Bottom-up processing isn't about preconceived notions or other ideas we have about the stimulus. This type of processing is simply, cut-and-dry, about what we are processing directly from the stimulus.

As you listen to this music, your frontal cortex is constantly predicting what will come next and forming new expectations based on what you've already heard. For instance when listening to a pop song, you somehow "know" when the chorus is about to happen. When you listen to a symphony you somehow "know" when the movement is about to end. If you've heard the song before, you know for sure what will come next when you listen to it again. Bringing this "bias" to the table when listening to music is referred to as top-down processing: what you already know is influencing how you perceive the stimulus.

So when we listen to music, both top-down and bottom-up processing are hard at work. As your brain analyzes the individual features of what you're listening to (extraction), you are processing bottom-up. However, the constructed representation of the music, as well as inferences made about it, are thanks to top-down processing. Schemas (mentioned in previous post) also result from top-down processing.

Think of it like this:

Bottom Up: Sensory input gets sent and sorted in Brain (extraction)
Top Down: Brain affects perceived input and makes sense of it (integration)