User Manual
FLAC
FLAC stands for Free Lossless Audio Codec which is an audio coding format for lossless compression of digital audio, and is also the name of the free software project producing the FLAC tools, the reference software package that includes a codec implementation. Digital audio compressed by FLAC's algorithm can typically be reduced to between 50 and 70 percent of its original size and decompress to an identical copy of the original audio data.
FLAC is supported in OnSong on iOS versions that support the codec which appear to be iOS 11 and higher only.