After installing Lilypond 2.20.0 and Frescobaldi 3.1.1 Lilypond is logging:
Starting lilypond-windows.exe 0.4 [filename]... I uninstalled and went back to Lilypond 2.18.2 and Frescobaldi 3.0.0 but I am still getting the same message. Music seems to be processing OK, but this seems strange. Thanks, Mark