OpenScore is a crowdsourced initiative to transcribe the world's public domain sheet music into an open source, digital format. This brings music notation into the 21st Century, enabling its convenient use on devices such as phones, tablets and computers. OpenScore extends the principles of open source to apply not only to software, but also to the content produced by the software, thereby opening up a new avenue of funding for open source software development. OpenScore was announced to the world exactly 2 years ago at FOSDEM 2017. Since then we ran a successful Kickstarter campaign to digitize famous classical works, and transcribed over 250 19th Century Lieder as part of OpenScore Lieder Corpus. We return to FOSDEM now to update you with our progress so far, share details about some of the key challenges and hurdles faced along the way, and look ahead to the bright future of open source sheet music. OpenScore was created as a collaboration between MuseScore, the leading open-source music notation program, and IMSLP, the largest online archive of public domain music. The IMSLP archive contains scanned copies of public domain scores by Mozart, Beethoven and other classical composers in “binary” PDF format, which allows musicians to read them, but not edit or listen to them. OpenScore unlocks the scores’ true potential by making the actual musical “source code” available in MuseScore’s text-based format, which enables listening, editing, and easy conversion to MusicXML, MIDI, PDF as well as image, audio and video formats. Text-based scores offer improved accessibility over PDFs, and are easily parseable by software tools to allow searching, indexing, data mining, and analysis for research purposes. All OpenScore transcriptions of public domain works are released under Creative Commons Zero (CC0), ensuring they remain in the public domain where they belong. OpenScore partners: MuseScore, IMSLP, RNIB, Nicholas Rougeux (c82)