OAPENThe OAPEN Foundation is a not-for-profit organisation based in the Netherlands, with its registered office at the National Library in The Hague. OAPEN is dedicated to open access, peer-reviewed books. OAPEN operates two platforms, the OAPEN Library (www.oapen.org), a central repository for hosting and disseminating OA books, and the Directory of Open Access Books (DOAB, www.doabooks.org), a discovery service for OA books. We work with publishers to build a quality-controlled collection of open access books, and provide services for publishers, libraries and research funders in the areas of dissemination, quality assurance and digital preservation.
This link will take you to the page where all their 100+ books on music are in various languages.