LilyPond

LilyPond is free music engraving software that takes a different approach from every commercial alternative: music is written as text in a source file and the software engraves it, rather than being placed on screen with a mouse.

That sounds obscure and is deliberately chosen, because it inverts the usual priority. Graphical notation software asks the user to position elements and produces a result that looks like what they arranged. LilyPond asks the user to describe the music and produces engraving decided by typographic rules, which is why its output is regularly compared to hand-engraved plates from traditional publishing rather than to other software.

The practical consequences follow from the text format. A score is a plain text file, so it can be version controlled, diffed, generated by a program, and read in fifty years by anything that can open text. Anyone who has tried to open a twenty-year-old proprietary notation file will recognise why that matters.

The cost is a genuine learning curve. Writing music as text means learning a syntax, and the feedback loop is compile-and-view rather than immediate. For someone entering a simple lead sheet that is worse than a graphical editor; for someone engraving a complex score to publication standard it is frequently better, because the typographic decisions are made consistently rather than by hand.

The project publishes an introduction, examples, manuals and a community, and frames freedom as its own topic, which is the software freedom sense rather than the price.

LilyPond is free with no licence cost.