How to Convert Encore Scores to MusicXML and Import its MusicXML to MuseScore
I've converted and imported roughly 900 Encore and Overture scores to MuseScore via MusicXML and I've summarized some important advice and reliable steps into the attached PDF, which I plan to update occasionally.
That said, musicXML is not your only option if you're trying to open Score Writer or old Overture scores! For one you could export to MIDI—there are serious pro and cons to that. But far better than musicXML or MIDI, MuseScore can open many formats directly, including Overture .ove files (scores created with Overture 4 or earlier) and .scw files (scores made with Score Writer.) Score Writer and Overture are by SonicScores.com
And the next point is significant: MusicXML does not export note velocity. As mentioned in the attached PDF, on MusicXML import MuseScore sets all velocity types to OFFSET = 0, so playback velocity is completely flattened.
If you want your Encore velocities in MuseScore you need to export to MIDI which will reliably convey them, but this is at a twofold expense:
a) you'll lose many of the score elements and layout details that MusicXML can commute but MIDI cannot.
b) when using USER velocities you won't be able to influence MuseScore playback with dynamic marks—dynamic marks in MuseScore only affect OFFSET velocities.