A good way to spice up your lines and add a melodic twist to your phrasing when soloing over the II m 7- V7- I major 7 progression is to employ the melodic minor scale.
The bII7 chord is a common substitution for the V7 in a typical llm7- V7- I chord progression. The bIIm7 chord functions as a dominant substitution for the V7 chord because both chords share the same tri-tones. Both chords resolve nicely to the tonic chord. G7 and Db7 share the same tri-tones
Because the bII7 chord has a non-diatonic root, your lines take on a slightly altered tonality and flavor. Use the Ab melodic minor scale from the 5th degree of the chord (example-if the bII7 chord is a Db7, then count up 5 notes to Ab). The same scale can also be called Lydian b7 from the root of the bII7 chord.
The following examples utilize the melodic minor scale over the bIIm7 (Db7) which resolves to the I major7 chord. Examine the use of arpeggios, scales, and guide tone resolution. Some of the examples are written an octave lower.
Use the following examples to get the sound of the scale in your head and then begin creating your own phrases. Be sure to write all of them down in a music notebook for future reference. Transpose all of your ideas into all 12 keys. Good Luck!