If you want to experience Just Intonation first hand then please visit the Online Terpstra Keyboard and experiment for yourself. This was originally created by James Fenn. I have added a few additions and will continue to build upon his wonderful work. You can even use this on an iPad or tablet of your choice in order to use multiple fingers for chords and scales.
Make sure “Enumerate Scale” is not checked, scroll to the bottom and click on “MAKE ME A MICROTONAL KEYBOARD!”.
Click around to hear how this Just Intonation scale sounds. If you’re on a laptop or desktop then hold down the space-bar for sustain, or if using a tablet then shake it until you see a message that says “Sustain On” You can turn sustain off by shaking it again (working out the details on that).
To play a Harmonic 7th chord play the following notes: R, 5/4, 3/2, 7/4. What you have here is a very stable and consonant chord that is unavailable to you if playing on a piano in 12ET. This is only a very small beginning of what awaits you in new musical sounds and textures.