Will there be a possibility to attach files on the mobile version?
Today this is based on drag & drop to a field, and this is not possible on an iPad.
We also need to be able to attach FLAC and Zip files as accepted file types.
WAV, DSF and DFF?
My two suggestions should cover it all. If zip is allowed as an attachment, once can zip any file desired. FLAC is handy as it is a standard and is already compressed. (Any WAV file is better uploaded as FLAC as it is smaller. The user can convert to WAV as desired.)
DFF and DSF are essentially the same for consumers, but DSF allows for meta-data. I would go with DSF. However, the files are huge and few possess any ability whatsoever to edit them, even for size. I see little use for either as a result, but it certainly does not hurt to have the capability to upload them.