According to some sources, Tadd Dameron's "Lady Bird" was written in 1939. This sparked a few thoughts. The melody in measures 3-4 is a version of the well-known "Honeysuckle Rose" lick, deriving from Fats Waller's 1929 tune of the same name, and a favorite II V phrase of the 1940s bebop players (often played with rhythmic or melodic variations). If the 1939 date is correct, it's the earliest use of the lick that I know of, after Waller's original song - though I'd imagine players quoted it plenty in the 1930s, since the tune was a pop hit.
Here are the changes to "Lady Bird":
I had always thought of the Fm7 Bb7 in bars 3-4 as IVm and bVII dominant, two chords borrowed from the parallel minor key (C minor), rather than as II V in Eb major. But here Dameron uses a II V lick as melody, indicating that he was thinking of the harmony in bars 3-4 as a II V in Eb. This shift of tonality from C to Eb, a minor third up, would not be unusual for Dameron. Note also that he follows this in bars 7-10 with a shift from C into Ab, a major third down. All of this makes me think that II V in Eb is probably what Dameron had in mind for bars 3-4, not "parallel minor."
Yes, it's true that Eb major and C minor share a key signature, and use the same set of notes - but they are not the same thing; they sound different. Using one key or the other, or thinking of the sequence as a II V, will lead one to come up with different types of solo ideas. Taking a cue from the melody, is II V maybe a better way to go in this case?
The IVm bVIIdom progression is sometimes called a "back door II V." I've never felt quite right about using this term. For one thing, IVm and bVIIdom are not always used together, but quite often are used singly, and can substitute for each other. In many or most Broadway-style standards, IVm and/or bVIIdom do not suggest a key change, but are there to provide minor color to a prevailing major key. In that kind of setting, they are best explained as "chords borrowed from the parallel minor." Classical music has long used this device.
The IVm bVIIdom progression is also sometimes classified under the heading "subdominant minor" - a group of chords that use the b6 note, the strongest note for bringing minor color to a piece that is otherwise in major. Subdominant minor chords used in C major would include Fm6, Fm7, Bb7, Abmaj7, Ab7, Dm7b5. They can often substitute for each other.
"Modal interchange" is another term used for this sort of device: i.e., switching from major mode to minor mode. Using this term, we can add G7b9, G7#9, G7"alt" and G7 #5 to the above list (I can't quite bring myself to label a dominant, V-type chord as "subdominant minor"), since they import notes from the parallel minor.
In "Joy Spring," written by a jazz player (Clifford Brown) rather than a Broadway composer, the melody and chords in measures 4, 12, and 28 seem to reflect a treatment more like Dameron's - that is, the melody employs a II V lick over the IVm bVIIdom. I don't hear any key change here, but the melody in these spots is definitely a II V shape.
All this musing led me to check out some classic solos on "Lady Bird" and "Joy Spring," to see if I could find any indications as to which way the soloists might have been thinking. I checked Clifford Brown's and Harold Land's solos on "Joy Spring," Miles Davis' solo on "Half Nelson" (1947, same chords as "Lady Bird"), Fats Navarro's solo on "Lady Bird" (first recording, 1948, with Dameron), and Dexter Gordon on "Lady Bird" (1964, 9 choruses).
Below is my take on what these great players were doing over the IVm bVIIdom sections in "Lady Bird" and "Joy Spring." The players' names are linked to the transcriptions that I consulted - thanks to the musicians who did the transcribing, including Jeff Rzepiela for the Harold Land solo!
Clifford Brown on "Joy Spring" (transcription is in concert key, F; trumpet solo starts at 1:45 of the video) (the measure numbers below are not as shown on the linked chart; my numbers do not include pickup measures):
m.4 - Notes are plausible as a "back door II V" (Bbm7 Eb7), but Brown may be treating this measure as he would a C7 (V in F), playing a b9/#9 lick over it.
m.12 - Brings out the D, the parallel minor-signifying b6 note in this section, but the line is plausible as a II V.
m.28 - Plausible as a II V, but again reflects a possible b9/#9 over an imagined C7.
m.36 - The D natural doesn't really fit the Bbm7. Could be a missed note, but would fit an imagined Gm7 C7 with b9/#9 over the C7.
m.44 - F# minor scale (parallel minor in this section).
m.60 - Brings out the Db (parallel minor note in this section); plausible as a II V.
Harold Land on "Joy Spring" (transposed for Bb inst., shown in G; tenor solo starts on 0:55 of the video linked to above for the Clifford solo) (again, measure numbers not as shown on chart; mine do not include pickups):
m.4 - Seems to be an obvious II V lick
m.12 - Bebop scale II V lick
m.28 - II V lick
Miles Davis on "Half Nelson" (same chords as "Lady Bird") (transposed for Bb inst., shown in D; recording is here; trumpet solo starts at 1:21):
mm.4-5 - Melodic shape somewhat follows the outline of the "Honeysuckle Rose" II V lick.
mm.19-20 - Scalewise with F# pickup; plausible as a II V (Gm7 C7) lick, with #9/b9 over the C7.
Fats Navarro on "Lady Bird" (transposed for Bb inst., shown in D; recording is here; trumpet solo starts at 0:32):
mm.4-5 - Chord-oriented with "enclosure" shapes; he is probably thinking II V.
mm.19-20 - Runs Gm7 to the 9, possibly a II V idea.
Dexter Gordon on "Lady Bird" (transcription in link, described below, is in concert key, C; video is here, with visuals showing transcription in D, transposed for Bb inst.):
mm.3-4 (chorus 1) - Seems to be thinking Fm7 for both measures
mm.19-20 (chorus 2) - Same
mm.35-36 (chorus 3) - Eb note moving to D suggests II V
mm.51-52 (chorus 4) - Perhaps II V
mm.67-68 (chorus 5) - Quotes head (Honeysuckle Rose II V lick)
mm.83-84 (chorus 6) - Eb major material (suggests II V)
mm.99-100 (chorus 7) - F "blues scale" lick, both measures
mm.115-116 (chorus 8) - F blues lick and Fm material
mm.131-132 (chorus 9) - Eb note suggests parallel minor, but Dexter might be just thinking Fm7 for 2 bars again.
Summing up - In these recordings, the II V interpretation is the approach most utilized over the IVm bVIIdom. In the case of these two tunes, "back door II V" might be an apt term. However, II V doesn't seem to have been the only way these players' thoughts went. Sometimes we hear a parallel minor shape, as in m.44 of Clifford Brown's solo, or a b9 #9 that would normally go over a C7 (V) even though the chords are Bbm7 Eb7 (IVm bVIIdom), as in mm.4, 28, and 36 of Clifford's solo. Or a player might just run the IVm chord, as Dexter seems to be doing. It all works. As always, if it sounds right, it is right.
Here are the changes to "Lady Bird":
Yes, it's true that Eb major and C minor share a key signature, and use the same set of notes - but they are not the same thing; they sound different. Using one key or the other, or thinking of the sequence as a II V, will lead one to come up with different types of solo ideas. Taking a cue from the melody, is II V maybe a better way to go in this case?
The IVm bVIIdom progression is sometimes called a "back door II V." I've never felt quite right about using this term. For one thing, IVm and bVIIdom are not always used together, but quite often are used singly, and can substitute for each other. In many or most Broadway-style standards, IVm and/or bVIIdom do not suggest a key change, but are there to provide minor color to a prevailing major key. In that kind of setting, they are best explained as "chords borrowed from the parallel minor." Classical music has long used this device.
The IVm bVIIdom progression is also sometimes classified under the heading "subdominant minor" - a group of chords that use the b6 note, the strongest note for bringing minor color to a piece that is otherwise in major. Subdominant minor chords used in C major would include Fm6, Fm7, Bb7, Abmaj7, Ab7, Dm7b5. They can often substitute for each other.
"Modal interchange" is another term used for this sort of device: i.e., switching from major mode to minor mode. Using this term, we can add G7b9, G7#9, G7"alt" and G7 #5 to the above list (I can't quite bring myself to label a dominant, V-type chord as "subdominant minor"), since they import notes from the parallel minor.
In "Joy Spring," written by a jazz player (Clifford Brown) rather than a Broadway composer, the melody and chords in measures 4, 12, and 28 seem to reflect a treatment more like Dameron's - that is, the melody employs a II V lick over the IVm bVIIdom. I don't hear any key change here, but the melody in these spots is definitely a II V shape.
All this musing led me to check out some classic solos on "Lady Bird" and "Joy Spring," to see if I could find any indications as to which way the soloists might have been thinking. I checked Clifford Brown's and Harold Land's solos on "Joy Spring," Miles Davis' solo on "Half Nelson" (1947, same chords as "Lady Bird"), Fats Navarro's solo on "Lady Bird" (first recording, 1948, with Dameron), and Dexter Gordon on "Lady Bird" (1964, 9 choruses).
Below is my take on what these great players were doing over the IVm bVIIdom sections in "Lady Bird" and "Joy Spring." The players' names are linked to the transcriptions that I consulted - thanks to the musicians who did the transcribing, including Jeff Rzepiela for the Harold Land solo!
Clifford Brown on "Joy Spring" (transcription is in concert key, F; trumpet solo starts at 1:45 of the video) (the measure numbers below are not as shown on the linked chart; my numbers do not include pickup measures):
m.4 - Notes are plausible as a "back door II V" (Bbm7 Eb7), but Brown may be treating this measure as he would a C7 (V in F), playing a b9/#9 lick over it.
m.12 - Brings out the D, the parallel minor-signifying b6 note in this section, but the line is plausible as a II V.
m.28 - Plausible as a II V, but again reflects a possible b9/#9 over an imagined C7.
m.36 - The D natural doesn't really fit the Bbm7. Could be a missed note, but would fit an imagined Gm7 C7 with b9/#9 over the C7.
m.44 - F# minor scale (parallel minor in this section).
m.60 - Brings out the Db (parallel minor note in this section); plausible as a II V.
Harold Land on "Joy Spring" (transposed for Bb inst., shown in G; tenor solo starts on 0:55 of the video linked to above for the Clifford solo) (again, measure numbers not as shown on chart; mine do not include pickups):
m.4 - Seems to be an obvious II V lick
m.12 - Bebop scale II V lick
m.28 - II V lick
Miles Davis on "Half Nelson" (same chords as "Lady Bird") (transposed for Bb inst., shown in D; recording is here; trumpet solo starts at 1:21):
mm.4-5 - Melodic shape somewhat follows the outline of the "Honeysuckle Rose" II V lick.
mm.19-20 - Scalewise with F# pickup; plausible as a II V (Gm7 C7) lick, with #9/b9 over the C7.
Fats Navarro on "Lady Bird" (transposed for Bb inst., shown in D; recording is here; trumpet solo starts at 0:32):
mm.4-5 - Chord-oriented with "enclosure" shapes; he is probably thinking II V.
mm.19-20 - Runs Gm7 to the 9, possibly a II V idea.
Dexter Gordon on "Lady Bird" (transcription in link, described below, is in concert key, C; video is here, with visuals showing transcription in D, transposed for Bb inst.):
mm.3-4 (chorus 1) - Seems to be thinking Fm7 for both measures
mm.19-20 (chorus 2) - Same
mm.35-36 (chorus 3) - Eb note moving to D suggests II V
mm.51-52 (chorus 4) - Perhaps II V
mm.67-68 (chorus 5) - Quotes head (Honeysuckle Rose II V lick)
mm.83-84 (chorus 6) - Eb major material (suggests II V)
mm.99-100 (chorus 7) - F "blues scale" lick, both measures
mm.115-116 (chorus 8) - F blues lick and Fm material
mm.131-132 (chorus 9) - Eb note suggests parallel minor, but Dexter might be just thinking Fm7 for 2 bars again.
Summing up - In these recordings, the II V interpretation is the approach most utilized over the IVm bVIIdom. In the case of these two tunes, "back door II V" might be an apt term. However, II V doesn't seem to have been the only way these players' thoughts went. Sometimes we hear a parallel minor shape, as in m.44 of Clifford Brown's solo, or a b9 #9 that would normally go over a C7 (V) even though the chords are Bbm7 Eb7 (IVm bVIIdom), as in mm.4, 28, and 36 of Clifford's solo. Or a player might just run the IVm chord, as Dexter seems to be doing. It all works. As always, if it sounds right, it is right.