... duplicates or not to be scanned next time. First scan may take a while depending on your PC and number of audio files, but on subsequent scans only newly added files will be scanned.
IL Music Library Deduplicator is portable and doesn't require instalation and also is free. It is written in Python and is using Chromaprint fpcalc for audio fingerprinting. It can find duplicates even if audio files have no metadata or have a different filename.