Audio formats a classic iPod supports
A classic iPod only supports MP3, M4A, AAC, WAV and ALAC. Other formats can make the Music menu show “0 songs”.
Unsupported formats
The iPod cannot play FLAC, WMA or OGG. If files in those formats are present, the iPod indexer can fail.
What iPod WebSync does
It detects incompatible files before copying them. With a pass it can convert FLAC to 320 kbps MP3 and add them to the queue.
Sync your iPod from the browser, nothing to install.
Open iPod WebSync