Changes

Let's play all of the different intervals- fret the 2nd string using your index or middle finger, and make sure it's curled enough so the the 1st string is left open and can resonate at the same time as the 2nd string. Pluck both strings at the same time, sliding up one fret on the 2nd string each time:

We start on E on both the 1st and 2nd strings. The 2nd string moves up one fret semitone each time: F, F{{s}}, G, G{{s}}, A, etc. This allows us to hear all the intervals named in the tables above; however, we are hearing them all against the root note of E, not C.

The line below the tab indicates the interval. Notice how nasty the {{Mn2|m2}} and {{tt|tt }} intervals are. the {{M7|M7}} can also be a bit nasty, but because there's more space between the notes, it sounds less harsh. On the other hand, the {{P4|P4}} and {{P5|P5}} sound very harmonious. The other notes sound less and less so going from the major 3rd/6th, minor 3rd/6th, and major 2nd/7th.

Notice in the table of all the intervals I've included columns for Just Intonation Ratio, Just Intonation Cents, and 12-Tone Equal Temperament Cents. If you don't know what the hell I'm talking about, don't feel bad. The J.I. Ratio merely indicates roughly how harmonic each interval sounds, with the smaller ratios more harmonic than the larger - this follow the experience of playing the tab above. [[Equal Temperament and Alternate Tunings#Cents|Cents]] are a strict measure of relative pitch that are covered way later on. I merely want to pique your interest now - guitar is a fun instrument in allowing us to play with pitch and harmony in ways other instruments cannot. Mastering the instrument goes beyond simply knowing the strict intervals listed above but knowing the math and core concepts of harmony as well as how to achieve this in your playing. For now you should be mainly concerned with the sound and names of the intervals, not the pairs of notes involved in the tab. For example, you should know what a perfect 4th interval sounds like in comparison to a minor 3rd, but not worry about knowing that E-A is a perfect 4th and E-G is a minor 3rd. ''That will come with time. Don't stress!'' Eventually, you'll want to be able to know all the intervals in terms of every note. Like this:

Inside any particular major scale, every note has a different set of intervals for all the other notes in the same key. In C Major, C and A both have major 2nd, perfect 4th, perfect 5th intervals but have different 3rd, 6th, and 7ths. If we added a harmony line a 3rd above the melody, we'd have a major 3rd when the melody played C (C - E), but a minor third when the melody played A (A - C).