When I try to play a piece of music, it is like training. Training to master the melody, the movements, the quality of the sound, and all other aspects of playing music. A teacher will instruct the way to play these notes.
My question: Is this initial training a connectivist way of learning? Is it rhizomatic? Or a more broad question: Is it possible to define all learning (riding a horse, writing Chinese signs, understand black hole theory in astronomy) in a connectivist way?
Questions 
Jaap, thanks for this wonderful question. My short answer is yes, all learning is connectivist in nature.
For me, both training and learning are processes of pressing against reality—always unavoidable, sometimes intentional—which result in patterns of knowledge within our own bodies. A musician, for instance, presses her fingers against her instrument, and her fingers and ears and mind learn patterns that approximate some pattern in her mind, which is the result of earlier pressings. I talk more about this on my blog at Communications and Society.