Watch the Cascading Harp Harmonics: 1 online guitar lesson by TrueFire from Play Acoustic Guitar 8: Advanced Techniques
Cascading Harp Harmonics: 1 - Concept 15 is a video guitar lesson presented by Brooks Robertson and is sourced from Fingerstyle Survival Guide.
This technique was pioneered by great players such as Chet Atkins and Lenny Breau. It can be used for a wide range of sounds, beautiful textures, accompaniment or even lead and solo application. What's special about the harp harmonics is that the technique gives you the ability to voice chords in a way that is otherwise impossible on the guitar plus it can give you a beautiful, ethereal, harp-like quality. Although both hands must work in unison to achieve the desired sound, the right hand (picking hand) technique is the most critical and is what you should focus on first. Once you have a grip on the picking hand portion of the technique and have a few patterns memorized, it's time to focus on combining that with some left hand concepts.
Having the proper form and technique is essential in getting the most from the harp harmonics. Your tone, accuracy, speed, consistency and volume will come from having the fundamentals correct. Watch the videos a few times, paying close attention to the straightness of the index finger and the rigidity of the thumb. Be aware of positioning of both the thumb and index finger. The index finger of the picking hand lightly touches the string, twelve frets higher than whatever is being played on that specific string with the left hand (fretting hand), the thumb is what actually picks the string, sort of tucked back in the palm of the hand. The more distance between the thumb and index finger the better tone and sound you will get.
Practice with only one string first. Keeping the string open and placing your index finger (of the picking hand) over the 12th fret. Try getting the harmonic to ring out clearly. Keep your index finger nice and straight. Remember to barely grace the string with your index finger. Now move to some of the other open strings and try the same thing. Once you are able to consistently get good tone, volume and a clean/clear harmonic to ring out then move on to outlining a chord form. You should be striving for good tone and accuracy before speed. For example if you play an E major chord with your fretting hand, this means you must outline the same chord/shape 12 frets higher, with your index finger of the picking hand. Refer to the video if you do not understand this.