Wow, how long did this take?? I lack the dedication necessary to finish such an involved project D:

As a side note, I thought Augustine was a guy until the last panel where she kisses the king. I was very, very confused for a moment there xDDDD

That was very nice! I don't recall reading about this particular fairy tale ever, so it was a double treat.

The colours and their use to divide sections of the story were great! However, the long black-bordered section that crosses between the first two pages looks a little muddier than the rest of the pages. I think in the first panel it might have been better to make Augustine's clothes green to stand out more, and to have the walls a different colour than that purple, which blended in with the combination of red and brown around it. In the second panel, the black background brought down the colour, in which I assume was supposed to be vibrant and expressive, quite a bit. Though I know with traditional art the scanner and monitor can really change how the colours appear, and it's not like they can be changed anyways.

Augustine's identity did not come to me before page eight, and I haven't been surprised by a "really is a girl" twist in a while, so mission accomplished! If you really wanted to make sure not a single person made it to the end not knowing the truth, you may want to hide more of that curly hair under the hood in that close-up, but it does blend into the hood well enough, and it's good foreshadowing and a reward for the observant. I think it added quite a bit to the story, and you were clever in handling it.

The writing did not quite flow in some places, but those instances grew far less frequent as the story went on. Now I'm no writer, but they mostly seemed to revolve around the subject. {For example: on the page with the queen reviewing the letter, the text opening with "The letter" is a bit confusing, because it directly follows a bit about the child lute player.} On the other hand, there are parts where a pronoun could be used. {For example: on the first page you have "Augustine was born. - Augustine loved"} I get the need to avoid gender-specific pronouns in half the narration, but using a variety of improper nouns like "the child" and say, "the young entertainer" could help break it up a little more, or even finding a way to combine and manipulate the sentences so that Augustine wasn't the subject at all could work.
Always remember to read your scripts out loud to yourself to make sure they sound 100% right. I often don't do this, and I am a worse human being for it.

It reminded me a lot like the kind of stories to be found in Flight books: [link](comics)
They are very much worth looking into, both to study as a comic maker and artist and to just plain read and appreciate.
If you have a book store with a graphic novel collection worth its salt go in, take a look, and read a story or two.
I will recommend going in and reading The Changeling for Volume 5, Onere and Piccola from Volume 7, Riddle from Volume 8, and The Clockmaker's Daughter, also in Volume 8 (Actually just after Riddle!). The plots of those four stories are a little bit more fantastical than the Lute Player's, but the story, setting and art all share a sort aesthetic with your comic here.

So yeah. Keep making comics, because comics are great and you are great.