This one is for those who are passionate about music fonts.
SMuFL is a standard for music font interoperability. SMuFL stands for "Standard Music Font Layout".
We were previously using "Emmentaler", which is the default font for the software LilyPond.
We have planned some time ago to use the SMuFL standard, so it would be easier for you to choose which font you would like to use on Flat. The leap is now taken, we use the Bravura, which is the reference implementation for SMuFL.
Cyril & The Flat Team