some improvements in "find song by content" and a new search mode for a single duplicate download BETA: https://www.zabkat.com/test/declone.zip
there's no installer, just download, unpack and run
* registry tweak msSongStart defines how much of a song to read for comparisons. The default 15 sec is good balance between time of exacution and false positives. So best left alone
* FIND ONE SIMILAR FILE
In expert mode, it is possible to add a FILE along with the folders to scan (using drag-drop into FOLDERS TO SEARCH box). This special search mode will only find files that are duplicate/similar to this added file, using whatever options you have set. This quick mode allows you to check a new file against a treated (decloned) collection.