Notator

Notator is a sheet music processor that turns human-readable source text into nice sheet music.

Features include:

• Human readable syntax
• Scriptable
• Outputs PDF, PostScript, SVG and PDF
• Single source file contains all information for the full score and all the parts
• Extracting parts is fully automated
• Can reuse voices for multiple parts, in multiple transpositions and clefs without having to copy/paste anything
• Transpose on-the-fly
• Macros
• Automatic barlines
• Understands several music fonts:
  • Maestro, Engraver and Petrucci from Finale
  • the MusicalSymbols font that shipped with Windows (or maybe Office?) decades ago and can be found on the net somewhere
  • the shareware Fughetta font (although this one does not include all the dynamics glyphs, so Notator emulates these)

And, as usual, it's Free Open Source Software, released under a BSD-style license.

https://bitbucket.org/tdammers/notator/

Here's an example of what it can do: