Version 6.1.0

• Update MEI schema to 6.0-dev (6da4dd5071303ac53d73d7b5ea0399f9cfe7bdba)
• Support for stageDir
• Support for ASCL custom tuning (MusicXML import and MIDI output)
• Support (initial) for notationtype@tab.staff-like
• Improved key signature changes in sections with restart
• Improved MusicXML importer (@vgrp, fingering, symbol)
• Improve mixed beams with stems up and down
• Option --mensural-responsive-view multi-valued ("auto|none|selection")
• Fix bugs in the CMME importer
• Fix --remove-ids option invaliding expansions