I've learned quite a bit about playing chords on violin and I do know I can harmonize by adding instrument voicings, plus notate guitar & piano chords/progressions on my PreSonus Notion Mobile app (mine is android version). 

I did look for 'Harmony Generators', a while back.  Didn't find anything stand out for android, but a VERY interesting app is still available for iphones/ipads - "HarmonyWiz".  

HARMONYWIZ is an advanced harmonic generator which can create multi-part harmony, all just from inputting a single musical line. You can paint your music in or play it from a piano style keyboard. You compose it and HarmonyWiz will arrange it! 

...have to admit I never looked to see how relevent 'Vocal Harmony' apps might be.  

Decided I better make sure I learned about ALL the types of harmony, especially since I want to do something creative with the little tune I composed a few months ago ('Wistful Thinking') & also just had my new Spark 2 'smart' amp delivered - so, I've been spending some time looking for ways to see harmony differently (and will share anything I end up creating).  

Stuck Writing 4 Chords? How To Write Better Harmony - voice leading (Inside The Score). 

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