Rhythm as the Illusion of a Predictable World
According to recent cognitive theory, the basal ganglia is the region of the brain that is used to judge short time intervals. Striatial spiny neurons in the basal ganglia are surrounded by oscilating neurons which pulse between 10-40 times per second, out of synch with each other.
When the spiny neuron fires a timing pulse, all the oscilators synchronize and track the lapsing of time. When an interval is to be remembered, the substantia nigria sends a burst of dopamine to the spiny neuron, signalling it to record the cortical signature of that precise moment by remembering the relative timings of all the oscilating neurons it listens to.

One spiny neuron may have 10,000 to 30,000 dendrites connecting to the surrounding oscilator neurons. When a time interval is to be reproduced, and its conclusion predicted by the basal ganglia, a burst of dopamine is sent out simultaneously with the spiny neuron pulse. Then the spiny neuron recognizes the upcoming cortical signature from the previous timing experience and sends a signal to the cortex through the thalamus of its prediction.

The experience of rhythm is essentially the ultimate ego boost for the basal ganglia. The regularity of an established rhythm makes the brain subconsciously count off and predict upcoming beats and signal to the cortex that it is onto a pattern. If we are sitting still, we may subconsciously start tapping our foot in prediction (and confirmation) of the rhythms that our brain is chiming to. Our basal ganglia creates a sensation of falling forward to a predicted landing place. If we are walking, our brain may subconsciously entrain our gait to synchronize with the perceived regularity. It is this sense of falling toward a predicted outcome that makes us want to dance. Dancing is the urge for us to move our bodies toward the lure of a predicted beat. Our basal ganglia senses the impending convergence of rhythms and our bodies sympathetically move in synchrony, emphasizing (indeed celebrating) our predictions.

Our minds are always watching time. Some oscilator neurons are watching it quickly while others count it off slowly. The stimulus of musical rhythm however causes this witnessing to become cognitive. Whenever our attention is intruded upon, the striatial spiny neurons start pulsing and regulating to make sense of patterns in perceived intervals of time.

It could be said that our brains are captivated by rhythms because of the profound sense of symetry and predictability they create in our perception of our surroundings. Perhaps the brain, pulsing with electric and dopamine ticks in time with the beat, feels like a student who knows all the answers to the teacher's questions. Or perhaps it is a sort of puzzle to our minds as we seem to be captivated by a recurring deja vu of repeating moments. Our mind is enraptured by the perception of firm and predictable regularity in an otherwise chaotic mix of timings. Perhaps we delight in the momentary illusion of a predictable world.