3:17 - Capo On The First Fret

To be in key with the original recording, we need to put a capo on the first fret.
Now, when I make reference to positions on the neck, I make them in respect to the position of the capo. Though the capo is on the first fret, I treat it as the nut or the 0 position.

3:58 - Chords In First Key

This song does something that I haven't seen/heard in any other song. It modulates to three different keys so that the second verse is played in an entirely different key than the first verse and the third verse is played in an entirely different key again.
So, although there are only three different chords for a verse, there are three different keys for the verses.
You can see this when looking at the pdf link above.
The first verse is in the key of E and the chords are E, B7 and A.

5:48 - Chick A Boom Rhythm

This is a classic Johnny Cash rhythm which he uses in many of his songs.
It is counted as 1 &a 2 &a 3 &a 4 &a.
The down strokes land on the down beat and &. The 'a' is an upstroke.
In terms of strumming, you could refer to it as down, down, up for every beat so that a four beat measure would be:
down down up| down down up| down down up| down down up

Often times the down beat will only be the root note of the chord or the fifth of the chord.
The &a will be full chord strums.

You can use the syllables Boom Chick A Boom Chick A to verbalize the rhythm.

You can find the lesson for this particular melody in the rhythm guitar video series here:
Eighth Sixteenth Note Rhythm

8:26 - Humming The First Pitch, Pickup, and Progression

When Johnny changes key for each verse, he needs to find his new reference pitch and if you listen closely you can hear him humming the root note of the new key. This is the first note of the melody in the new key.

The melody starts on the second half of the third beat - & 4 & = I Keep A (first three words of the lyric).
These notes are part of the I chord. The progression then goes directly to the V chord.

Each chord lasts for a single bar.

The progression is as follows (chords for the first verse):
V7 I = B7 E
V7 I = B7 E
IV I = A E
V7 I = B7 E

The second verse is in the key of A.
The third verse is in the key of D.
The fourth verse is back to the key of A.
The first verse is then repeated in the original key of E. On the recording, this verse is sung a full octave lower than the first time through. Good luck with that.

18:55 - Transitioning Between Keys

To transition smoothly from one key to the next, a short three note melody is used.
The transition starts on the & of 3 similar to the start of all the verses and happens right after the previous verse.

25:04 - Lead Guitar Intro

There's a great and relatively simple guitar lead right off the top.
Below are the guitar tabs for this lead taken from the pdf link above.

30:25 - First Full Play Through

Taking it slow and working through what we've learned.
There's no harmonica yet. That comes next.

34:50 - Melody On Harmonica

Learn how to play the melody on harmonica.
We'll pick out a key and go through the tabs.
The guitar is playing chords in the key of E but because the capo is on the first fret, that puts us in the key of F.
Therefore, since I am playing in first position, I am playing an F harmonica.

40:04 - Putting It All Together: Full Play Through With Harmonica

Now let's put everything we learned all together including lead intro, all verses with transitions and ending it off with a harmonica solo at the end.

43:43 - Lead Guitar Melody

If you'd like to learn how to play the melody on lead guitar, we'll pick out a key and then work through the melody.

And there you have it - Johnny Cash's I Walk The Line.

Stay In Tune. Peace.
George