Roast my landing page

The main issue is when you land in the page, there's a lot of text. I get overwhelmed as a user (cognitive overload bias). Better to work on a lighter hero banner, with a simple value proposition, two or three lines of text clarifying what you do (What's in it for them) and a call to action. Not having a clear call to action within the first scroll may increase the bounce rate and you may be leaving a lot of users on the table.

Brand identity-wise, I believe you are in the right direction, it can be improved and better defined but definitely looks harmonic.

I am probably not your ideal customer, however….

I find the homepage colour scheme too sombre. It feels deflating, whereas the best home page experience would be the opposite.

The headline is too obscure and not sufficiently compelling. Instead of :“Compose, Visualize, Iterate: Where Your Musical Ideas Take Form“, this part of your sub-headline carries more interest: “Reception AI helps you craft the story your composition is telling“.
Even then, you are not selling clearly in a succinct headline the benefits users would get from your product. Getting the language right and being able to communicate your offering in a way which resonates with your customers is a crucial “stay or go” decision for site visitors.

This article by Matt Lerner is a very useful explanation of why the language you use needs to fit the market you are trying to sell to:

https://review.firstround.com/finding-language-market-fit-how-to-make-customers-feel-like-youve-read-their-minds#how-to-find-the-language-that-picks-the-lock-or-why-nobody-wants-your-all-in-one-solution#introduction

To answer your questions directly:

“Is it clear what the tool does?” No.
“How's the call to action?” There’s nothing to persuade me to take any action - where’s the incentive?
“Do the colors resonate?” No.

Overall, I find myself asking: “Why would anyone buy this?” What exactly is the value it brings to me, and how much will I have to pay for it. There’s no mention of either tangible benefits or price.

Hope this helps.