modes (and chord scales that come by association) are overrated.

in short, there are modes that correspond to each diatonic chord in a chord progression, for example in a key of C major, Dm = dorian, Em = phrygian, etc... each diatonic chord still uses all the same notes, but of course each note means something different relative to each chord's root. the reason i think they are overrated is because i think it's better to view each diatonic chord through it's parent scale. so if we label the original C major scale do-re-mi-fa-sol-la-ti, the Cmaj (ionian) chord will be do-mi-sol, Dm (dorian) will be re-fa-la, etc. this way it will be easier to hear the color of each chord in context relative to every other diatonic chord from the same family, no need to switch modes (or chord scales) to deal with each chord separately.

and then there is modal music which makes a different diatonic chord your tonic chord, which is its own beast. for this one it's easier to think of two families of modes, minor and major ones. minor modes = minor scale with some alterations, major modes = major scale with some alterations. for example, for dorian we'd just sharpen the 6th relative to the minor scale. in turn, that changes the qualities of diatonic chords, for example in dorian that makes the 4 chord major, when it would usually be minor for a regular minor key.

I had the same issue previously, but as @Dima G was saying, in the end what matter is on which degree of the parent scale you are.

What is cool about naming modes though, is that they really have a specific sound, and after you learn to hear them, they really feel like different flavours. So it's good to know that if you're on the second degree, your scale will be dorian, so you know whether you want to go up this scale or not when playing. Or if you're on the fourth degree, you know that playing up the scale would sound lydian (magical and fairy-like) and that's because of the sharp fourth, so when improvising, you know that if you don't want that sound, you just have to lower that sharp fourth or avoid playing the fourth note altogether and leave it open to interpretation by the listener.

I think there is a reason most classical and much of modern music stays in the major/minor realm and rarely strays into modes. Modern/classical harmonies, melodies, and chord progressions do not need modes to make sense, and our ears are used to those sounds and therefore uneducated music consumer enjoys them better as they can relate better to the music.
IMHO modes are better left as a way to create something unique, rather than something to study and use extensively.
I personally enjoy some modal music, but generally when the only parts of the music is simple melody, chords, and rhythm (little/no harmony) I think modes are currently best used in scales for riffs or folk song tunes, however that does not mean that composers/songwriters should be confined to this, I would love to hear a large modal orchestral piece, I just personally never have.

In jazz, the modes are helpful to know as available notes for improvising over a chord/chord progression. I struggle with this, but recognizing the sound of the modes is useful.

modes are useful for improvising over chords as terri says. they also are just good ways to practice major/minor scales since they are essentially the same thing just with another starting point.

like if you've really mastered the major scale, you should know it up and down the fretboard/keys/whatever from any starting point, not just the root. and practicing modes strengthens that. it also makes it easier to find your way back to the root from any given point

so, even if you don't find yourself actively using them, they are still very useful as a part of your practice

It is possible to talk a lot about the subject. At some point, any music learner will come across the modes... Unfortunately, most of the immediate sources on this subject that we come across say very little. It boils down to something like “starting the C major scale from any of its notes and working its way up to its repetition an octave higher”. It is very easy to convince ourselves that their presence in music theory is nothing more than a historical curiosity, or that they contain inscrutable secrets that, once we reveal them, everything will make sense and we will become better musicians as we dreamed. In fact, they are both of these things at the same time, but the most important (and interesting) thing is what lies in the middle of these two extremes.

One of the things we are not told is that modes were not simply used as we know them. The Lydian, for example, translated into our modern diatonic language as F – G – A – B – C – D – E – F, had the B lowered by a semitone, so that a tritone did not occur (which made this mode similar to the Ionian). In fact, the B flat is the only change that we will find in the keys of medieval and Renaissance music. The change was noted with a round/soft symbol, mole (mollis in Latin). When B was in its natural version, it was represented by a square figure, which is why it was known as hard B (durus, in Latin). Also, square in latin is quadrus, in Portuguese (my mother language) the natural symbol is called bequadro. Hence you can see where the B-moll and B-dur come from for B-minor and B-Major in Germanic nomenclature.

The Dorian, in turn, reached its tonic by a half step, which caused the C below to be raised by a semitone, becoming C#, the leading tone of D. This is the same thing that happens in the harmonic and melodic minor scales. In A minor, A – B – C – D – E – F – G – A, the G was changed to G#, to create the leading tone of A, and the F to F#, so that there would not be an augmented second interval between F and G#.

The effects of the treatment of modes have always been seen in music. If I have, in C Major, a chord progression C – Dm, and I want to add a secondary dominant before Dm, I will have the progression C – A – Dm. A does not belong to the diatonic chords of C Major, but belongs to the chromatic (or altered) ones, brought by the tradition of modes. If I want a C – Am progression, and I want a secondary dominant to emphasize the Am, I will have C – E – Am. The E will have, as its third, a G#, leading tone to A. It is the same procedure that was done with the Dorian ( and the Aeolian, whose sequence of five initial notes belongs to the same interval proportion as the Dorian). The Lydian mode, for example, which had its fourth changed half a step lower so that a tritone was not formed, added the Eº chord to the harmonic field of C Major as a III chord. F – G – A – B – C – D – E – F became F – G – A – Bb – C – D – E – F. Therefore, overlapping the thirds, E – G – Bb.

So, we see how secondary dominants are, rather than a dogma, or an invention someone took from nowhere, a historical development of musical practice. Take the cadence widely used in Jazz, including for secondary tones: IIm7 – V7 – I, for a major chord, or IIm7(b5) – V7 – Im for a minor chord.
Suppose we want to prepare the IV in C (that is, prepare the F chord, arriving at it through a secondary dominant). [IIm7 – V7)] – IV. It will be: Gm7 – C7 – F. The use of a secondary preparation and dominant does not mean that we modulate to the key of F, but that we use the C Mixolydian mode to do so. (Bb instead of B in C Mixolydian).

If you observe the harmonic field of any and all modes, it will be nothing more or less than the harmonic field of a natural major mode, but transposed. Which means you can introduce a modulation by melodic means, making use of notes characteristic of a mode.

For example:

C major: C – Dm – Em – F – G – Am – Bº.

D dorian: Dm – Em – F – G – Am – Bº - C = Same chords as C major (which can also take you to A minor).

C dorian: Cm – Dm – Eb– F – Gm – Aº - Bb = Same chords as B flat major (which can also take you to G minor).

E Phrygian: Em – Fm – G – Am – B° – C – Dm = Again, same C major chords.

C Phrygian: Cm – Db – Eb – Fm – Gº – Ab – Bbm = Same chords as Ab major.

So, there are specific ways to treat each mode so that it maintains its characteristics and does not take you, as a result of its interval relationships, to another tonality without your wanting it. And, having control over these processes, you can introduce altered notes into a melody of, for example, C Major (a very common one is to go down the C Major scale with C – Bb – A, so that Bb is a descendant leading tone to the A, while ascending we go to C with A – B – C), and with that opening the way for, harmonically, a new tonality to be established. In this case, Bb will open immediate doors for you to F major and D minor.

Also, using the modes allows for unique sounds. Listen to Renaissance music, and you will hear beautiful sounds that cannot be achieved in any other way than by the treatment of modes.

Yeah, to add to what Andrew and Terri are saying, I think the positioning relevance is more pronounced on a fretboard than on a keyboard, but if you're playing anything Jazz or fusion adjacent you probably spend a lot of time with the modes not only for improvising but for writing riffs.

Someone else (Edit: Igor, of course!) would likely know more (I studied drums primarily so didn't pursue the line of thinking from this lesson for that long) but I'm fairly certain you can do cool substitutions that aren't strictly diatonic as long as your scale still includes the accompanying chord tones in their appropriate position. For instance the band plays a Major triad on the tonic, but the soloist flattens the seven to play a bluesy mixolydian lick. Or aeonian and dorian, for another example.

But honestly I shouldn be talking about this it's above my paygrade lmao

On a very practical note. Some of the different modes I know the sound of them but I always count when I hear a scale - either ascending or descending - I know at which point in the different modes there are. Minor thirds, minor seconds, raised sixth etc. that may be helpful for you as well

Great explanation @igor reis

Huh... So much to grasp :) Thank you for all your input!

Thank you @igor reis for that really interesting and helpful explanation!

@Question Toothbrush thank you for asking questions, @igor reis thank you for that amazing post!!!

@Terri Winters @Jesse Lyons @Benjamin Jack You are always welcome!

I'm sure I've only scratched the surface, as I have plenty of material on modes just waiting to be digested. I tried not to confuse you any further on the matter. I hope you saw more possibilities in them, such as resources and work materials, than realizing that there is another Everest to be climbed on this journey which is music! Well, and if it's one too many Everest, what's the problem, anyway?! 😅