What are some alternatives?
When comparing GUITAA and GetHarmony.net, you can also consider the following products
Chordify - Chordify turns any music or song (YouTube, Deezer, SoundCloud, MP3) into chords.
yalp.io - Automatic chords extraction from mp3 and YouTube
ChordU - Extracts chords from any song, integrated YouTube.
Guitar Dashboard - Open-source interactive music theory for guitarists.
Chord Generator - Used to draw guitar chord images.
Amazing Slow Downer - !A slow down music software for Mac and Windows computers - Amazing Slow Downer