B Flat Mixolydian
Here's an interesting lick to add to your arsenal! It outlines the Bb7 sounds, with some passing tones (non-diatonic notes) to spice up the mixolydian scale. Transpose the phrase to other keys!
The lick is built around the Bb Mixolydian scale and begins with variouws chromatic passing tones. Notice the F-7 arpeggio at the end and the resolution on the third (D note) of the Bb7 chord.
Use the neck pickup and cut the high freqs with the tone knob if necessary. I use the Mesa Boogie V-Twin preamp on the clean channel connected directly to the sound card and I'm adding a little bit of reverb in Pro Tools.