"Hear, O heavens! Listen, O earth! For the LORD has spoken" (Isaiah 1:2).
Barry Webb says, "These opening lines are like the first stirring chords of the overture to a great oratorio. They summon us to listen and give us the first indication of the character of the work we are about to hear."
And like a great piece of music, there may be several movements which will sound different. Isaiah is like that. This prophet ministers over several decades and so of course there are many different movements within this great piece. But he says it himself in 1:1 - "The vision..." Not, the visions, but one vision.
Isaiah - a grand piece of many movements. But all one piece. All one composer. All one vision.