Reading/watching interviews with some noted jazz/rock musicians (e.g., Jimmy Bruno), when asked about modes they will disavow themselves of bothering to study modes because doing so is, to their way of thinking, unnecessary. These are all fine players, and I'm not taking issue with them (one way or the other). What I'd like to know is: Do people who feel this way essentially solo (improvise) differently (and if so, how) or do they essentially get to the same notes in a different way? (Do players who employ modes sound different than those who don't? )
Take a II, V, I progression in the key of C. Here's two ways to approach it.
Over the II chord, play dorian, over the V play mixolydian, over the I play Ionian. I personally don't like thinking this way. I prefer the second way, to think "key of C" and listen to the unique sound of each chord and define those chordal notes. This may be what these players are referring to.
You should of course be defining the chord tones with arpeggios and using substitutions etc. Like over the V chord, playing an altered scale, whole tone, diminished etc. Before doing any alterations however you need to get your arpeggios and scales related to the key cased all over the fretboard. This can take years (sorry).
What if you're playing over a cycle of fifths though? Yes, you'll need to have mixolydian under your fingers.
What if you're playing a modal tune with no strong resolution like V to I? Yes, you will need to play that mode if you want to bring out the sound of that mode. Simply finding the related Major scale is not a great idea as you need to listen for and define the sound of the mode the tune is in.
It's also important to play each mode and get it under your fingers to get used to the each mode's unique sound. After all, you make music by using your ears and manipulating these different sounds. It's difficult if not impossible to intelligently make music if you're not really hearing it and you don't understand it...
Jimmy Bruno is an extremely competent and technical guitar player who would definitely know all about modes from a performance viewpoint. If you could provide the quote I could give you a better answer but here's what I think he's talking about.
Players like Carol Kaye and Joe Pass form solos from chord notes with connecting notes. There are a couple of reasons for this.
First, the notes of the underlying chords are the strongest possible notes you can play, especially in jazz where dominants and complex chord voicings rule.
Second, in jazz, reharmonization on the fly is the rule rather than the exception so in a group setting when the chord changes are every two beats it's easier and even better to improvise solos on the underlying chord tones rather than expend the mental resources to try to break down each group of chords into a key center and related mode. From an academic viewpoint, yeah, you think about modes but it's better for a performance setting like this not to explicitly practice modes. Your ideas are going to be more in accord with the piece if you play off of the chord tones. On the other hand, you may decide that you want your solo to float above the changes and in that case explicitly thinking about modes might help.
On the other hand, players like Miles Davis play modally and so their solos are all about the mode, not the underlying chords which tend to be very basic. (See "So What" for example.) In this case, you would definitely practice your modes because you aren't going to be getting many ideas from the chords.