Dynamics

MuseScore follows general audio standards and uses dynamic range normalization to bring the loudest part of the score up to the same level as other scores. This is done routinely so that in radio broadcast or playlists, you don't hear extreme differences in volume from piece to piece.

If you wish to disable this, you can uncheck "Normalize" in Edit / Preferences / Export.

I just took a look at your piece.

I think the problem is that your crescendo hairpins do not have louder dynamic symbols after them. Instead, they simulate them visually using end text.

For example, let's take a look at your crescendo in measures 8–9. It contains end text that looks like a “𝐩𝐩” dynamic symbol but doesn't actually do anything. The last actual dynamics symbol before the crescendo is the “𝐩𝐩𝐩” in measure 1, and the first actual dynamics symbol after the crescendo is also a “𝐩𝐩𝐩”, in measure 10.

As a result, the the crescendo goes from “𝐩𝐩𝐩” to “𝐩𝐩𝐩”; that is, it does absolutely nothing.

To fix this, you can do either of the following:

1. Remove the end text from the crescendo and put a real “𝐩𝐩” dynamics symbol after the crescendo.
2. Edit the crescendo and set the Velocity change value to 17, which is the difference between “𝐩𝐩𝐩” (16) and “𝐩𝐩” (33).

Whichever way you decide to go, make sure you edit all the crescendo hairpins in your piece.

For more information, see Playback of hairpins.