If your melody track is a midi file, you can convert the track to an Artist Performance File which is audio, open the Audio Edit Window and open the Edit Menu |Harmonize and this will give you access to the Harmony List of 255 selections and also the option to place each harmony part on its own track.
If your melody track is an audio file, everything is the same with the exception you don't have to convert the track to an Artist Performance File.

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BIAB 2025:RB 2025, Latest builds: Dell Optiplex 7040 Desktop; Windows-10-64 bit, Intel Core i7-6700 3.4GHz CPU and 16 GB Ram Memory.