As part of their All The Years Live video series, the Grateful Dead's archival group posted a video of the group's performance of the song "Fire On The Mountain" (along with a substantial amount of the preceding "Space" section) from October 31, 1980, the final night of their concert run at Radio City Music Hall in New York City. It's the same version released on the live compilation Dead Set, which means it may well be the first version of the song I ever heard since Dead Set was one of the earliest Grateful Dead recordings I ever got. (The first was the 1987 studio album In The Dark, which didn't do much for me; the second was the 1972 live album Europe '72, which most definitely did, especially the "China Cat Sunflower>I Know You Rider" and "Truckin'>Epilogue>Prelude>Morning Dew" segments.)
It reminded me of something I'd been wanting to write something about: lead guitarist Jerry Garcia's remarkable melodic variation in the song. The song itself is made up of a simple oscillation between two chords: B major to A major. In terms of key signatures, the song is, then, quite clearly in the key of E major, where B is the dominant and A is the sub-dominant. In terms of modes, the most inside scale choices are B Mixolydian over B major and A Lydian over A major. Since both are modes of the E major scale, staying with its seven notes is the simplest choice. Garcia does sometimes use these—but not all the time. At other points, he uses B Ionian (i.e. B major), with its A sharp, B Lydian, with its E sharp, and A Ionian, with its D natural, revealing of his gifted understanding of and capacity for melodic variation.
Below, I've written out the various modes along with transcriptions of composed moments where Garcia makes use of different modes with times from the video. The section beginning at 3:36 is interesting as he varies the mode, D natural vs. D sharp, in what is otherwise an exact repetition. I also really like the ending riff, beginning at 9:18, with its prominent A sharp that provides such an effective contrast with the many A naturals that have come before as well as the A major chord that follows.
Another example of Garcia's facility for melodic variation is in the song "Cumberland Blues." From its beginning all the way up to the end of the bridge, around 4:30, he sticks to G minor pentatonic. At 4:32, however, even though the harmony is the same G dominant seventh as before the bridge, he shifts to G Mixolydian, with its B naturals rather than the Bb/A#s of the minor pentatonic. It gives a whole different sound to the song and is a better fit for the later chord changes.
