Let it Grow – Grateful Dead

tldr: Let it Grow is primarily in A minor but has two key changes, to D major and E minor. It starts in A minor with Am7 – Bdim (i – ii°). The lead is A aeolian over the Am7 and B diminished scale over the Bdim, primarily the Bdim chord tones. Then Am Bdim partial chords and Csus2 (the III chord) twice, with a G – Bm – D transition to the key of D major. The G is the VII chord of A minor, but also the IV of D, and the Bm is not in A major but is the vi chord of D major, so that shared G chord eases the transition between keys.

In D major, there’s a D – A7 back and forth, ending in a Bm, then back to a variation of the Am – Bdim – Csus2 progression, only this time ending in Esus2. The first time you hit this, it goes back to the beginning. The second time it marks a key change to E minor. Two rounds of a progression of Esus2 B G Esus2, which is i – V – bIII – i, with the V chord borrowed from E harmonic minor. After the first time, there’s a C to Bm ending; after the second, a Bm, A, and then a harmonized walk down the scale from G, and back to what we’ve done earlier.

Eventually there’s a long jam at the end, first over Am7 – Bdim, with lead largely in A aeolian or A dorian. Then the rhythm goes to Em, signifying a change back to the key of E minor, and the lead is largely in E dorian.

Let it Grow

Among the 7 diatonic chords in a key, there is one diminished chord: the vii° chord in a major key and ii° in a minor key. Often ignored or replaced by a minor chord, here it’s a star. Let it Grow is in the key of A minor and based around the starting chord progression of Am7 to Bdim, which is i to ii°. Bob plays it with partial chords in the middle of the fretboard:

  Am7           Bdim
---x------------x----0-----0--
---8------------6--6-----6----
---5--(strum)---7------7-----7
---7----------9-9-------------
---0------------x-------------
---x------------x-------------

Arpeggiate (is that a word?) the Bdim chord by slowly dragging your pick across each of the three strings. The extra part at the end isn’t necessary, but I heard it in one of their performances and it sounds cool. Jerry leads over the Am7 with the normal minor aeolian scale, but plays a B diminished scale over the Bdim. While you can work in other scale notes, the key part is the chord tones of a diminished chord, each of which are a minor third apart, or three frets distance horizontally. Even just doing this sounds cool over the Bdim and is the core of what Jerry does:

------------13---------------
------12-15------------------
--/13------------------------
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-----------------------------
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Any note three frets to the right or left of any particular one of these works too; they will all be the notes B, D, F, or G#, which are the notes of a diminished chord (including the diminished 7th note).

Then there’s a movement from Am to Bdim partial chords to Csus2 (III chord) twice (you can let the high E and B open strings ring along the way if you want), followed by a transition from the G chord (VII chord) to Bm to D:

--------3------3--2--2-------
--------3------3--3--3-------
--5-5-7-5-(x2)-4--4--2-------
--7-7-9-5------5--4--4-------
--------3------5--2--5-------
---------------3-------------

The D represents a temporary key change to D major. The Bm and D chords aren’t diatonic to the key of A minor (that would be Bdim and Dm, respectively), but G and Bm are the IV and vi chords of D major, so they transition well to the new key. In the new key, there is a little I – V7 progression with D and A7 (and the major chord A7 cements that we aren’t in A minor anymore) followed by Bm, and then we go back to the key of A minor, where there is a variation of the Am to Bdim partial chord thing from earlier. I’ll call this “Transition” to refer back to it later:

-------------------3--/7-----
-------------2-----3--/7-----
--5-5-7--5-5-3-----5--/9-----
--7-7-9--7-7---2-0-5--/9-----
---------------3-2-3--/7-----
-----------------------------

The first 2-3 thing is the same Bdim partial chord, just closer to the next chord for speed purposes. You aren’t chained to any particular chord voicing though, whatever works. The next 2-3 to 0-2 part is a partial C chord to partial Bm/Bdim chord to a Csus2, then ending in a Esus2. The Esus2 is not in key and suggests a transition is coming, but the first time we go right back to the start and do it all again. The second time through the Esus2 represents a key change to E minor. Without the third, the Esus2 itself is ambiguous, but the rest of the chords here are from E minor. There’s an Esus2 – B – G – Esus2 progression all at the 7th fret (the G chord is x109787). That’s i – V – bIII – i, with the V chord coming from E harmonic minor, which raises the 7th note. That is followed the first time by C (the bVI), Em7 (the i), and Bm (the v) at the low end of the fretboard. Then the Esus2 – B – G – Esus2 again, followed by Bm, A, and a harmonized walk down from G back to the part I labeled “Transition” earlier, which is back in the key of A minor. This walk down part goes:

-------5---------------------
-7-10--6---------------------
-7-7---7--4-2-0-0------------
-9-9---7--5-4-2-0-2p0-2-0-2--
----------------------3-2-3--
-----------------------------

After that, immediately go into the Transition part. The 10 is just a flourish note to the Bm chord; arpeggiate that and the A chord. The 4-5 starts the walk down (which also happens to include a good chunk of the main Friend of the Devil riff in the key of G).

Other than that, there is a long jam based around the Am – Bdim progression, only the Am is held longer and the Bdim more of a quick hit. The lead is largely in A natural minor (aeolian), though I also hear some A dorian and occasionally the raised 7th of the A natural minor. Then the jam modulates to the key of E minor, over an Em chord, and the lead shifts to E dorian largely, but maybe some aeolian too. Near the end there are two recognizable E dorian riffs. The first is something like E5-F#5-G5 repeated:

-----------------------------
-------------------------11--
--9-10-12--------------9-----
--9-10-12--9-11-12--12-------
--7-9--10--------------------
-----------------------------

And the other is essentially this riff, with some bends, harmonizations, and other variations.

--12b14b12--10-9----9b10b9---
-----------------12--------12
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--9-------9------------------
----10h12---12---------------
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