I searched through a lot Zune/Microsoft forums and people have been requesting this support for years but to no avail. Is there a work around? Is there a music player for Mango that can play FLAC format from OneDrive?
Another option is to mount a FLAC image (Surely you have matching .cue files for your .flac files) with Daemons Tools (free version perfectly suitable for the task) and ripping the virtual CD with WMP.
Try VLC For Windows Phone. It plays
.flac formats, and most media formats