ytx: How to write interesting chord progressions — Michael Keithson

Gist by njt containing a summary and full transcript of Michael Keithson's 25-minute YouTube video on harmonic theory for songwriters and improvisers.

summary.md — Key Points

• Harmonic thinking as a radial model: Keithson visualizes a key centre with multiple independent "strands" of harmonic options radiating from it, drawn from simultaneously when improvising or composing.
• Accumulating functional "strands": He started with only the seven diatonic chords and later added secondary dominants, modal interchange, two-fives, tritone substitutions, diminished chords, and five-chord alternatives as separate systems attached to the same key centre.
• Function over origin: Non-diatonic chords are justified by where they lead. Secondary dominants are "the V chord of each of the chords in our key"; diminished chords "function in very much the same way" as dominants.
• Transposability via scale degrees: For modal interchange, he remembers "chord types over scale degrees" rather than memorizing chords per key.
• Complexity as a tool, not a virtue: "a simple or boring chord progression doesn't invalidate a song." Different goals may be "hindered" by complex harmony.

Pithy Quotes

• "This visual, the key centre with the different strands coming off is quite a good representation"
• "For a while I was using some of these options in my playing, but without any real sort of understanding"
• "Different songwriters, musicians, composers, they're not all aiming for the same target"
• "having complex and interesting or atypical harmony might actually hinder trying to get the result that you want"

Tools & Methodologies

• Key Centre + Strands mental model — tonic at centre with radiating harmonic strands
• Secondary Dominants — V chord of any diatonic chord except the tonic (e.g., "five of two," "five of three")
• Modal Interchange — borrowing from three parallel minor modes (Dorian, Phrygian, Aeolian), memorized as chord types per scale degree
• Two-Fives (II-Vs) — preceding a dominant with its II chord; minor destinations use half-diminished II + altered dominant V; includes "backdoor two-fives"
• Tritone Substitutions — replacing any dominant 7th with one a tritone away (same 3rd and 7th inverted); shortcut: "whatever chord I'm heading to, I can put in a dominant chord a half step above"
• Diminished Seventh Chords — as dominant substitutes; play a diminished chord a half-step below any target chord
• Five Chord Alternatives — non-diatonic V7 replacements derived from manipulating a diminished chord built on the raised root of the V chord

Unanswered Questions (from summary.md)

• No decision-making framework for which strand to use when
• Voice leading is almost entirely absent
• Melody/harmony interaction never addressed
• Modal interchange oddly restricted (only Dorian, Phrygian, Aeolian) without justification
• Rhythm and harmonic rhythm ignored
• Five chord alternatives derivation is dense and under-explained
• No discussion of when not to use these techniques

transcript.md — Full Transcript

Channel: Michael Keithson Video URL: https://youtu.be/l_gV-2jU7zE Duration: 25m 10s Transcribed: 2026-05-15

(The transcript covers the full talk, beginning with Keithson's early days as a beginner exploring only diatonic chords, then progressively introducing each harmonic strand. He demonstrates each concept with piano examples in the key of C major.)

Strand 1 — Diatonic chords: "all the chords that exist natively in my key center"

Strand 2 — Secondary dominants: "none of these chords are diatonic to our key, but they all lead us to chords within our key." They are the V chord of each chord except the tonic. E.g., in C: A7 (V of ii) leads to Dm; C7 (V of IV) leads to F.

Strand 3 — Modal interchange (borrowed chords): "borrowing chords from any other key or mode that includes the tonic note of your original key and then returning back." He restricts himself to Dorian, Phrygian, and Aeolian. Memorized as scale degrees: ♭II = major 7, II = half-diminished, ♭III = major 7, IV = minor 7 or minor 6, ♭VI = major 7, ♭VII = dominant 7.

Strand 4 — Two-fives (II-Vs): Precede a secondary dominant with its corresponding II chord. Major destinations use minor 7; minor destinations use half-diminished II + altered dominant. Includes backdoor II-Vs and unnamed alternatives resolving to the IV chord.

Strand 5 — Tritone substitutions: Swap any dominant chord for one a tritone away — "they share the same third and seventh, albeit inverted." Practical shortcut: play a dominant 7 a half-step above any target chord.

Strand 6 — Diminished chords: Used like secondary dominants due to their close relationship (lower any note of a dim7 by a semitone to get a dominant 7). Shortcut: play diminished chord a half-step below any target.

Strand 7 — Five chord alternatives: Non-diatonic chords that replace the V7 and resolve to the tonic, derived from manipulating a diminished chord built on the raised root of the V. Includes four diminished chords, backdoor dominant (♭VII7), tritone sub (♭II7), and several half-diminished/minor 6 options. He excludes any alternative that loses the critical F→E (scale degree 4→3) movement.

Closing remarks: Keithson warns that "a simple or boring chord progression doesn't invalidate a song or composition," noting that different goals (lyrical storytelling, dance hypnotism) may be hindered by complex harmony: "Especially you jazz snobs out there, you know who you are."