I remember an interview with Tommy Chong.
He originally played guitar and toured in a few bands. Bobby Taylor & the Vancouvers has their own wiki page. Tommy was paying the bills gigging. Tommy said he began to realize it would take serious study to up his game improvising lead. He wanted to excel at whatever he did.
He switched to comedy, met Cheech Marin and soared to the top.
I think he still plays.
The “I don’t want to know theory” thinking always exasperates me a bit
I learned “theory” because I wanted to play Bach and couldn’t play it by ear
Learning “theory” gave me (as it turns out) more options than playing by ear had.
Scales - major - minor ( if you’re a guitarist you probably know these by “mode” anyway)
Keys - cycle of fifths - add a # each step (guitars don’t do flats) C -> G -> D -> A -> etc.
Keys 2 - If you don’t know the cycle of fifths see step 2
Learn to read music - even if you are really not good (I’ll vouch) it is really useful.
Fifteen minutes study of “theory” will save you years of widdling to an answer.
Francis Vaughan you make an excellent point about the jargon. Everything I read starts by assuming you already know what all of the nomenclature means. Which I don’t, which is what makes my eyes glaze over. Sure - I know what the words mean in everyday language, but not in the ways that are specific to music theory. Three notes a third apart - a third of WHAT? An interval. An interval of what between WHAT and WHAT?
And I have read of things like the Circle of Fifths mentioned above and the CAGE system only to look up and say WHUT?
We do all learn in different ways. That’s why I irritate the heck out of people trying to teach me things. I keep repeating what they say to me back at them in my own words until I get a “YES.” Avoids a lot of misunderstanding. But the jargon. Yikes, the jargon.
Think of a ladder. With a funny spacing.
For some reason, the drunk idiot that built the ladder made the steps 6 inches apart. Nice job for a drunk dude. 
EXCEPT there’s only 3 inches between the third and fourth steps. He also made the distance between the sixth and seventh steps 3 inches.
So, the ladder isn’t perfect. You can still climb it. It’s awkward and you’ll probably bust your ass, but it works. Blame the booze.
You’re on the the first step. You could easily put your foot on the third step.
If you really strain, you may get your foot on the 5th step.
You can even touch the seventh step with your hand.
That distance from the first step to the other steps are intervals in music.
You always think of starting on the first step. That’s your root.
That’s all there is to intervals. It’s just a distance from the root to the note you want to sing or play.
Those crazy ass 3" steps that carpenter used?
That’s always there in EVERY key.
Here’s your ladder. Notice there’s only one “.” between E and F. And one “.” Between B and C.
C…D…E.F…G…A…B.C
1…2…3.4…5…6.7…1
This ladder will always work. It’s the formula of a major scale.
Here it is using G as the root note.
This works because of a special rule in music. There’s always a half step between B and C, E and F. Just accept that rule. Some drunk ass carpenter made it up.
See how clever they are? Our formula tells us there has to be a whole step between 5 and 6. But music demands a half step between E and F. So, we kick F in the ass and shove it forward to F#. That’s the next fret on a guitar.
G…A…B.C…D…E…F#.G
1…2…3.4…5…6.7…1
That’s all there is to keys. You’re making the same ladder over and over again. Making certain notes sharp or flat to get that half step the drunk ass carpenter wanted.
The other cool thing is…
By kicking F forward to F# we got that required full step between 5 and 6.
But, even better we automatically get the half step between 6 and 7. F# to G is a half step.
It always works out that way. Why? I have no idea. It just works.
Try figuring out the the two sharps in D.
Here’s the letters. Build the ladder. Then figure out which ones have to be pushed forward to get the half step between 3 and 4, 6 and 7.
DEFGABCD
Then try the three sharps in A. You’re going to see a pattern emerge.
ABCDEFGA
I understand music but I can’t count.
The last half step is between 7 and 1.
It’s literally the final rung of the ladder before it starts over.
So heres the correction. All I changed is the gap between 7 and 1.
C…D…E.F…G…A…B.C
1…2…3.4…5…6…7.1
See, you still kick F forward to F#
G…A…B.C…D…E…F#.G
1…2…3.4…5…6…7.1
1 is the beginning of the next ladder. You can bolt three ladders together to reach the roof of a house.
In music each ladder is an octave.
As mentioned before, it all builds on previous knowledge, so it sounds like, if you really are interested in learning it, you’d have to start with the absolute basics and work up from that. It sounds to me like you’re trying to jump in too far ahead.
I’ve never tried the books, but something like “The Complete Idiot’s Guide to Music Theory” or “Music Theory for Dummies” seems to me like it might be a good starting point. If you have specific questions, we can help answer them here, but some terminology (like seconds, thirds, octaves, sharps, flats, etc.) will need to be learnt somewhere along the way, as these are the basic building blocks of discussing theory (or really just technical aspects of music in general.)
I really wouldn’t worry about the circle of fifths/fourths anytime soon, and I have no idea what the CAGE system is. Never heard of it. (ETA: Ah, apparently it has something to do with the guitar. I’m a piano/keyboard player. I mean, I futz around on the guitar, but I’m completely self-taught on guitar and never came across this.)
Btw, the pattern?
C no sharps
Key
G -F#
D - F# C#
A - F# C# G#
E - F# C# G# D#
and so on.
The odd ball is F. it has one flat. B flat
There are other flat keys. Most guitarists will never use them. Google is your friend if you need to look one up.
My piano teacher had us go through all the scales and figure out for ourselves which notes were sharp or flat.
It’s easy if you understand the ladder and how you must follow the formula for a major scale.
If you can at least figure out G and D then you got the general idea. Don’t make yourself crazy figuring out E.
Probably true, but you may already be playing flat keys if you like to tune the guitar to E flat instead of E (not too terribly uncommon. It’s all over the place in rock and blues.) But you’re most likely still thinking in terms of standard tuning. Also, if you plan to play with horns, you’d better get used to the flat keys, whether by using a capo, tuning down, or barring the heck out of most every chord.
Good explanation, except your half step should be between 7 and 1 (8), not between 6 and 7. 1…2…3.4…5…6…7.1
I wish that I could fix that numbering error. I put in a lot of work just to get tripped up on something so simple.
I heavily edited and consolidated the two posts into one document. I also suggest playing the G scale on the guitar’s G string. The D scale on the D string. A scale on the A string. So it’s apparent “…” represents two frets and “.” is one fret. Hopefully that will help people connect the scale numbers to the guitar.
I’ll put the finish doc on my Google drive. It’s the most simple explanation I could come up with.
I’d build that ladder (with 2x2’s) and drag it into class as a visual aide. A visual aide would be so helpful for people to see whole steps and half steps.
I left out the names of the intervals. No need to confuse someone with perfect fifths. That can be looked up or learned later. Chord building and chord progression can be learned later.
What’s important is visualizing the scale and understanding how the major scale formula is applied. Creating a scale from the formula is not something any musician does routinely. Do it once and you’ll understand it.
This article makes my head hurt. 
I would not want to pursue a music major in college.
I’ll post a link to the doc on Google drive later.
and they left out all diminished and augmented intervals. See https://en.wikipedia.org/wiki/Interval_(music)#Main_intervals"You sing the melody, and I’ll harmonize with diminished seconds"
Maybe someday I’ll understand why A to C is a third.
That’s one of those things we accept as the truth from teachers and books. Ace, Count the letters on your fingers, ABC is a third. Yes Ma’am that is a third.
But, if I walk from point A to B, then from B to C. That’s two units. Perhaps 2 ft, 2 yards, 2 meters. Whatever unit I’m using. That’s how you measure distance.
Anyway, I accept it’s different in music. Some things you just have to accept. Focus on the big picture and make music.
Even to me, that makes my head hurt a little. I don’t think of intervals in terms of half-steps between notes. I think in terms of the major scale (or not even much at all, as intervals kind of become second nature after awhile.) But everyone is different in how they learn.
One thing worthy of note is that the reason we have the sharps and flats where they are has everything to do with the layout of the black notes on the piano keyboard. In the key of C it’s very easy to see where the whole and half steps are.
Intervals are not really distance anyway. They are the difference between two frequencies, technically speaking.
And this in a nutshell is what I was driving at. The reason it is a third is the result of a few centuries of development in music that has been lost to most people. Yet the basic idea is the most critical part of understanding what it is you are doing.
Get yourself a single string, tune it to whatever note you want, but for the sake of the question, tune it to A (or just call whatever you tuned it to A - it doesn’t matter). Now measure a point of the string with the ratio 5:4 of the string’s length. Fret it there. You have your third. That’s it. At least in principle. If you build a full scale based upon your open string you will add other simple ratios, including the ratio 9:8, which is a point in between the open string and the 5:4. Add all the other ratios to get the basic scale (do, me mi …) just for completeness. The gap do to mi is your 5:4. I you want to label all the notes with letters it is A to C. Why is it called a third? Because C is the third letter after A.
It goes to hell and we lose sight of what is happening when we add all the additional grief and baggage needed to get ourselves to a consistent system of notes that supports transposition and a chromatic scale from which we can build all the other scales.
In simple terms, the interval that denotes a semitone above the tonic is 16:15. But, a semitone interval past that is the ratio 256:255, which is almost but not quite 9:8 (1.137 versus 1.125) And so on. You can’t take any note in the basic scale derived with these simple ratios and apply one of the other intervals to find another note in the scale. It is maddenly close most of the time, but it is provable from a pure mathematical point of view that you can’t do it. And some of the intervals actually miss badly.
There are a range of solutions. Go fretless, and play the interval as it was always meant to sound :D, or come up with various ways of making things even out. You will find keyboards that provide a significant extension past the usual 12 tone chromatic scale - they split the physical keys to account for some of the more important misses. Modern theory never tells you that D# is not the same note as Eb. But there are keyboards that split them. And the difference in sound is noticeable.
But anyway, we invented the equal tempered scale, and decided that as nice and as pure as the ratio system is, it is far too limiting. If you try to transpose on an instrument tuned using it you end up with appalling sounding intervals, because the ratios can’t work anywhere except in the fundamental key. So the answer was to wreck things, and divide the scale into exactly equal steps, defining the semitone as the base unit, and choosing it so that 12 semitone steps make an octave. (Which means if you multiply the semitone ratio by itself 12 times you get the ratio 2:1 - and thus the semitone is the 12th root of 2). Which is all fine and dandy, except that now not a single damned note is where it should be. The entire scale is out of tune, but the grief is spread around, and for many purposes things work, and the freedom for harmonic development is a huge step. So, now, no matter where you are, count 4 semitones, and the ratio is close enough to 5:4 that we are going to still use it, and we still call it a third.
It doesn’t all work well, and the fourth is the usual whipping boy for complaint. The miss when you use the equal tempered scale is significant. There is the notion that those of us immersed in the western equal tempered scale have never heard a real perfect fourth, and would be surprised by its purity of sound compared to what we are used to.
Can’t avoid mentioned the circle of fifths. This is another way of building the diatonic scale. Just take the interval 3:2 (the fifth) and keep going up in fifths, but dropping an octave (ie 2:1) when you get outside the first octave. Rather interestingly this yields another set of notes that are remarkably close to the ratios we were interested in. But never actually correct. You can buzz around and build up a scale, and when you return to somewhere close to the starting note you stop. Somewhere close is a matter of definition, but after 12 cycles you do arrive back at a point very close to the start, and that also gets us another approximation to the diatonic scale. But it is different again to any of the preceding. However if we define the fifth as 7 equal tempered semitones, we do get back to exactly where we stared after visiting each of the notes in the 12 tone scale. So the circle of fifths has dual use, as a way of deriving the frequencies of a scale (imperfectly) and as a basis for a pattern of harmonic relationships.
The nature of all the underpinning ratios we are trying to approximate yields a huge set of interesting patterns. The circle of fifths is just perhaps the simplest to understand. But the way the ratios weave in and around one another is more like some sort of huge mutidimensional spirograph pattern. You will see strong patterns repeating and these may correspond to various rote learnt rules. Sadly, because of the way you can’t build up transposing systems with the ratios staying right we end up with an approximation to the underpinning patterns, and sometimes that means even more rules to fix the gaps.
But really, any time, anywhere, you are faced with the concept of a third, the core point is that, within the limits of the instrument, and the tuning of the instrument, you are trying to get a ratio of 5:4. How you notate that is a matter of historical accidents.
Thank you. Actually, I should have said three frets up from the five to make that E-barre a “seventh.” --dominant, right?
The mistake you’re making is that A, B, and C are not points. They’re one unit wide distances. The entirety of A to C is three units.
Units of what?