7-Limit Just Intonation
7 Limit Just Intonation is when all the notes of the draw plate are in harmony.
The recipe to achieve this is laid out as a table of offsets but you cannot tune a harp to be in harmony using only numbers. No tuner is accurate enough - not to mention because of our embouchure, we skew the offset when we play individual notes.
This video is pretty much an audio-only example of what 7-Limit Just Intonation tuning is.
7-Limit-Just-Intonation favors the major chords over tuning the single notes. Any three consecutive holes played on the blow plate will play a major chord. Any three consecutive notes played on the draw side will play major chord tones but anything above hole five will include the flat-seventh and/or ninth. When tuned to 7-limit-Just Intonation, these chord tones are in harmony and imply the tonic.
You can call it a harmonic, a difference tone or a combination tone. When the frequencies line up perfectly, the effect is that the sum is greater than its parts. You get a louder more powerful sound.
See my other videos on tuning - as well as my Premium video on tuning using an analog strobe tuner - to learn how to tune using your ears to help build accuracy.