I've been using MuseScore for several years to arrange vocal and piano scores. It's really good!
The best thing about it being free is not so much that it is free for me, as the arranger (I've bought score editing software before). It is the fact that I can actually send the digital scores to the singers, and tell them they can use the same software for free to rehearse on their own (e.g., setting the volume of their voice louder, etc.).
One of the nice (tangential) things about MuseScore is that they provide and curate a really good MIT-licensed GM soundfont called Fluid[1]. (A soundfont is a collection of samples that usually gets mapped to MIDI instruments. Most built-in soundfonts are on the order of a few megabytes; this one comes in at a whopping 140MB!) The latest version is offered as an SF3 file, a modified version of the SF2 format where samples can be stored as OGG instead of WAV. The tool used to convert SF2 to SF3 can be found on Github[2] and is maintained by one of the lead MuseScore developers.
(I used the SF2 version of this soundfont in my new iPad music app[3], <shill> a kind of doodle-y, multi-instrument sequencer where you draw your notes directly on a pannable and zoomable canvas rather than plotting them out one-by-one like in most DAWs. You can draw notes at any point in time and bend them to any pitch, allowing you to easily play around with guitar solos and complex rhythms. It's sort of my modern take on sheet music. But I digress... </shill> Since the Fluid SF2 is so big compared to the SF3, I'm going to try to modify sftools to re-convert SF3 back to SF2 in order to keep my bundle size down.)
You can test it out by switching the play mode to "Synthetic" (click "Full mix" at bottom). Change instruments by clicking "Guitar" along the left margin.
I used LilyPond for quite a while, but I've found MuseScore just as powerful and much easier to use. Data entry is very simple once you get into the 4-C 5-D-# rhythm. I haven't contributed to the project--haven't found any bugs I needed to fix yet--but I am immensely reassured by the availability of the source code.
I find LilyPond has slightly prettier output, and is a bit more capable overall, but converting MuseXML to LY is easy, so I can write the score in MuseScore & make final stylistic changes in the LilyPond file if needed.
The output in their screenshots look nice, but it looks like there are some cases that aren't handled as cleanly as I suspect LilyPond would render them. In the "Praeludium 10" screenshot on their website, look at the first sixteenth note in bar 21, for example. It's rendered really close to the left margin (and obscures the tempo marking); most printed scores would include a tad more padding for readability. Would be interesting to read their layout algorithm and compare it to Lily's (I guess I can!).
Wow, that's weird. I downloaded the score in question (https://musescore.com/opengoldberg/scores/719586) and opened it in MuseScore, and found that for some reason that's the way the score's style controls were set. The "Barline to note distance" (under the Style menu in MuseScore, choose "General…", and then click "Measure" on the left) is by default 1.2 times the space between two lines of the staff. But in this score, it's 0.6! I have no idea why—changing that parameter back to the default seems to yield a much better layout.
There's also something else going on with that screenshot, though. The person who took it put page breaks in different places than in the actual score, which is why that tempo marking is overlapping. If you open that same score in MuseScore, the tempo marking is positioned appropriately.
If you're interested in score layout, Steinberg are working on a new score layout application with (from what I gather) a lot of emphasis on layout flexibility, and there are a series of blog posts about some of the more interesting and subtle score layout issues, including how the other major notation applications handle edge cases.
I don't know if it's just my browser (Windows Firefox) but the playback of songs seem a bit off. For example this one: https://musescore.com/user/3967646/scores/1673111 the red overlay is late by a few hundred milliseconds. Not much but it's quite noticeable.
It happens to me as well (Windows, Chrome) but inconsistently (sometimes, its on time). Looking at the JS, it might be since it schedules to check for updates every 100ms (`timerId = setInterval(update, 100);`) instead of scheduling a callback for the time of the next bar.
Edit: Also, the JS `setInterval` callback can be delayed.
Edit: After debugging their code some more, the above isn't why (though is still inefficient). The audio player (SoundManager) they are using only updates the audio playback time at a rough granularity. If I log the time values, I get the following (all in milliseconds):
0
182.404
681.59
1180.778
1680.963
2179.152
...
The song is 120 BPM which means that the first bar changes is at 2000ms causing the first bar change to be 179ms late.
Anybody know if/how well this can export scores to MIDI? I've recently been learning to use Ableton and found that exporting my compositions created in Finale to work excellently, which has given me a whole new level of control over it.
The best thing about it being free is not so much that it is free for me, as the arranger (I've bought score editing software before). It is the fact that I can actually send the digital scores to the singers, and tell them they can use the same software for free to rehearse on their own (e.g., setting the volume of their voice louder, etc.).