I notice this state quite often in myself. Not every night, but enough that it's not really notable anymore.
Usually, two seemingly unrelated concepts that I have been thinking about will become joined in strange ways — sometimes literally (some code I have been working on will be playing a song I have been listening to), sometimes in ways that I can't understand or describe.
Other times, I will hear music as loudly and clearly as if I were at a concert. It can be music that is actually playing, or not.
I find the experience pleasant and wish I could extend it.
Usually, two seemingly unrelated concepts that I have been thinking about will become joined in strange ways — sometimes literally (some code I have been working on will be playing a song I have been listening to), sometimes in ways that I can't understand or describe.
Other times, I will hear music as loudly and clearly as if I were at a concert. It can be music that is actually playing, or not.
I find the experience pleasant and wish I could extend it.