Cool. Dave McMurdo is a killing writer of straight-ahead charts...and all those T.O. cats can play their asses off. Where are you working with them - a workshop or school setting?
Anyway...to approach improv in a boppish sense, you need to maintain a sense of melody, harmony, and forward motion. It's tough to outline harmony whilst being melodic, with energy. SO, you need a clear idea of where you're going, and how you're gonna get there.
First - know the tune. Cold. Inside and out. Know the melody; know the form; know the changes; know the
words (?! ...yeah). There's kind of two aspects to improvisation: Linear, and vertical.
Linear is exactly that - thinking in a lateral motion, melodically, aiming two bars, 8 bars, a whole chorus, 4 choruses down the line.
Vertical is a more traditional approach - thinking in chord-tones and target notes.
Incorporating both aspects is key; maintaining a good line while nailing the changes...
Okay...the abridged chord/scale stuff:
Bop and most swing-based jazz-type music centres around a key. ii-V-I (see Autumn Leaves) or I-vi-ii-V-I (Oleo). You
can use the same scale over chunks of the form.
Gmin7 // C7 // FMaj7
Gmin7 = Dorian = 2nd mode of F Major
C7 = Mixolydian = 5th mode of F Major
FMaj7 = Ionian = 1st mode of F Major
No problem!
I - Ionian - Maj7
ii - Dorian - min7
iii - Phrygian - min7(b9)
IV - Lydian - Maj7(#11)
V - Mixolydian - 7
vi - Aeolian - min7(b6)
vii - Locrian - ø7 [ min7(b5) ]
Does this make sense? Here's a bit more depth in
this thread.
Another thing to be aware of is
each chord and its notes:
Gmin7 = G Bb D F
C7 = C E G Bb
FMaj7 = F A C E
Hugely important notes: 3rd and 7th. Find a tune with ii-V's...watch the 3rds or 7ths ...Oooh neat!
They flow...nicely. See above, our ii-V in F. 3rd of Gmin (Bb) , 7th of C7 (Bb), 3rd of FMaj (A). Beautiful. 7th of Gmin (F), 3rd of C7 (E), 7th or FMaj (E) ...again, smooooth.
Does this make sense?! Lemme know. If so, we can move onwards and upwards!!