Picture yourself at a point in time and space. In your head you have a vague sort of musical idea thing. In your hands you clutch a well-thumbed copy of this guide and a home-made map. You are at point A. Lots of trails lead off into the distance to mysterious destinations labelled Point B and Point C and all the way to the terminus, marked Nirvana. You set off to explore the trail to B but arrive at C instead, having got lost on the way. You retrace your steps to B only to arrive at D. Progress continues to be erratic, often circular, infrequently linear. Many a time you puff up a steep hill, occasionally you stroll down a pleasant vale. More than once you arrive puzzled at a complete dead end. Occasionally you find yourself on a different planet. Time loses its meaning, is it a couple of hours since I started, a week, a year, a lifetime? Now and then you rest, sleep, and, in your dream, take a birds-eye view of the journey. You look back at where you have been and marvel at having achieved so much. You look forward and scout out some options to get to the end. Some days you start the journey with a heavy heart, weighed down with gloom, crawling like a snail. Other days you take off like a rocket and conquer all before you. Eventually you arrive, tired but happy, in a sunlit meadow full of flowers.
Exploration is an excellent analogy for writing music. It also emphasises its most important feature: that it is an event that unfolds over time. A finished piece of music is not like a painting or a statue or a building or a photograph, it cannot be grasped in its entirety all at once. Writing music, and listening to it, takes time.