HarmonicAdder is a free pitch shifter and time stretcher VST, Audio Unit plugin developed by Anarchy Sound Software. Compatible OS(s): Windows 64b, macOS.
Creates harmonic resonances by pitch shifting the dominant frequencies in your input signal by the various intervals in the harmonic series (octave, octave+fifth, two octaves, two octaves+major third etc).
These harmonics can be mixed with the dry input signal to make it more resonant, or used on their own as a new sound.
http://anarchysoundsoftware.co.uk/anarchysoundsoftware/