MuseScore is great, I have used it to produce lead sheets professionally on several occasions and it does not disappoint. I grew up on Sibelius but prefer MuseScore for simpler tasks. They have done a great job.
I have a score for a choir in musescore and want to create practicing files. For example in the soprano file the soprano voice should be louder than the others. Do you know of an automated way to achieve this? Maybe via midi then ardour? I looked at some other tools like timidity but none seem to have the required api.
Though there's no built-in functionality in MuseScore to do this, you can write a plugin that controls the mix for each voice. See this forum topic, which is quite similar to what you're trying to do: https://musescore.org/en/node/56916
technically Ardour is free as in free speech, but not as in free beer. They do not have official binary downloads for free. If I remember correcyly its more involved than ./configure && make && make install Though Ubuntu Studio has a version ready to go.
Lots of software that's considered free-as-in-speech-and-beer doesn't have official binary downloads at all. Ardour additionally provides the option of paying to download an official binary. Building from source is pretty much the same as anything else, although there are quite a lot of dependencies. If you're used to installing from source there's no reason Ardour should give you any great difficulty (unless you're unlucky and your distro doesn't supply the required dependencies or something).