I told him, "Yes. The Cycle of General Thirds."
"Huh?" he said. "There isn't a cycle of thirds."
"Sure there is." I then proceeded to explain.
Professionals know what they know so well that they never think of simple things like this. First of all, The Cycle of General Thirds is CEGBDFAC. Why start with C? Why not? C is the the simplest scale on the piano. No black notes. And it's the scale all beginners start with, therefore, the simplest chord derived from the simplest scale is the C Major chord.
What's my line?
Students have the hardest time locating written notes on the musical staff. They may know that there's a bass staff and a treble staff; a left-hand staff and a right-hand staff, but then what? They probably heard that "Good boys do fine always," and that "Good boys deserve favor." But what does that have to do with anything?
Well, the first mnemonic tells you the names of the lines of the bass staff, and the other tells you the name of the lines on the treble staff. But, that presumes that you've gone to the (mild) effort of memorizing the names of just those two lines, G in the bass and E in the treble. Most students don't.
Now if you haven't noticed, each line on any staff that's higher than the one below it is a third higher. For instance, you know that the bottom line of the treble staff is E. Well, the next one has to be G, and the next one has to be B and so on. No mnemonic needed.
If you knew your Cycle of Thirds, and you knew your bottom lines, you then could just recite the cycle from the appropriate note. G on the bottom of the bass staff (GBDFA) and E on the bottom of the treble staff (EGBDF). Easy. Now you know.
Then, if you needed to read notes on ledger lines, those extension lines above or below the staff, rather than panic, you could just recite the cycle from wherever you were. For instance, the top line of the treble staff is EGBD... F. If, God forbid, you should have to play a note on the 4th ledger line higher than that F, all you'd have to do is say, FACE. The note is E. All because you know The Cycle of General Thirds.
Chords are what create harmony, and chords are made of 3rds. That means that, on the written staff, notes on 3 consecutive lines or on 3 consecutive spaces are chords.
Note: Make sure you practice blurting out the letter names in groups of three: "EGB, GBD, BDF," etc. The reason is that you don't want to have to stop and think about it. Reading is an instantaneous process, made instantaneous by repetition, just like knowing your phone number.
So easy! Right?
Yes and no. I said that this was The General Cycle of Thirds. What that means is that the letter names, in their fundamental form, will always flow according to the Cycle. That's letter names only. What it won't tell you is when you need to use sharps and flats.
That's bad right? No. It's perfectly fine. Remember, the student didn't even know how a chord was made up until two minutes ago. Just knowing this puts you miles ahead of where you were. Your recourse before would have been to memorize every chord as if it had no relation to anything else. And as we all know, rote learning is tedious and a wasteful use of time.
So please, if you're a student, do yourself a favor: Learn the General Cycle of Thirds. You'll understand harmony sooner and you'll learn to read music 10 times faster.