I would say that good knowledge of scales has been some of the most valuable musical development I have ever done. They help with improvisation, harmonic and melodic analysis, and creativity. Remember that harmony is built from scales, so hearing the sound of a sale goes a lot deeper than just a series of notes. If you aren't finding them useful then I digging deeper into them, learn to play them fluently, learn to sing them, after a while you will start to notice them coming out in your playing and writing. It is pure vocabulary!

So, that you CAN tell those differences and be sensitive to them, for one thing. This can help both in transcription and composition.

I 2nd David and Victor. I'm in the same place with learning to use it practically but I can finally start to understand the creative use of the different modes and how it's used set an emotional atmosphere.

For me, knowing the sounds of the various scales is helpful for playing in a jazz band and improvising. I can (a tiny bit!) recognize the color notes being used which helps me respond to a soloist, for example.

Just to elaborate a bit on my previous answer, just because you can't CONSCIOUSLY tell the difference between one scale and another doesn't mean they don't make a MUSICAL or EMOTIONAL difference. Aligning our conscious processes with our subconscious ones is what this whole process of learning music more deeply is all about. This allows us to enact our artistic intent more surely and deliberately. I definitely feel that I'm better able to hear when something isn't quite right (and separate that out from self-doubt that might be lying to me) and know what to do about it. Anything that trains you on recognizing the difference between different techniques, structures, and concepts helps with that.

It's useless if it's a sole focus of musicality development, it's ok as a niche supplemental practice.

In my opinion, for most tonal music (including jazz) it's way more important to hear pitches in-key within the major (or relative minor scale) of the song's key. All diatonic and non-diatonic chords come out from this same scale. For example, when you go through a simple 2-5-1, it doesn't sound like dorian into mixolydian into ionian (that's what chord scale people want you to believe but it's not the way it's perceived emotionally), it sounds like scale tones of the major scale rotating to follow harmony. It's particularly apparent when analyzing vocal lines or lyrical solos like But Not For Me by Chet Baker. Melodies flow elegantly through changes instead of jumping from one mode to another.

Another example is all the mixolydian/altered/diminished scales. Those definitely don't make any sense in isolation and should be looked at within the context of how they resolve, which in most cases again means within the context of some kind of a 2-5-1, major or minor. That way it's also much easier to see parallels between them all and how they all are different colors/variations of the V chord. Going deeper there are very curious intersections with other dominants from the family like tritone subs and backdoor dominants. There are a lot of shared scale tones when looked from this angle. But these patterns are impossible to see when looking at these scales in a vacuum.

Sure, there is modal harmony and modal jazz and modal vamps too, but it's not how most of the tonal music works.

Now, given that, the reason I don't like the Scale Spy is because it fails to put these scales in context. Like I mentioned, playing lines under the ii chord will not sound like a Dorian mode, even though technically the notes come from it. It will sound like you are playing around the chord tones of the ii chord, and there are functional implications of it then pivoting to V and then to I and it's a very big difference perception-wise from when we truly are in dorian mode.

If one goes through transcribing a 6-2-5-1 line with only 2 beats per chord and you try to hear each section of the line within the chord scale related to a chord (mixolydian/aeolian into dorian into mixolydian into ionian), you'll go nuts and/or probably will not truly internalize the line in the end.

TL;DR: there is a long-standing big confusion between purely modal music and diatonic modes/scales within tonal functional music.

Thank you all for your replies.

@Dima G that was a bit advanced for me, I'm afraid, but I appreciate the time you took to provide an answer.

@Adam Deering If simplified, the main point I was trying to make is that for most of the music it's more beneficial to see all the melody and chord changes coming from the major scale (with alterations where needed) instead of switching scales per chord. So if a song is arpeggiating through I-vi-VI-V progression you'd hear: do-mi-sol la-do-mi fa-la-do sol-ti-re. You will not move where do is on every chord.

And so with scale spy if you hear a mixolydian scale, you'll likely hear it (within the exercise) as do-re-mi-fa-sol-te-do, but instead you should be hearing it like sol-la-ti-do-re-mi-fa-sol. with a resolution to do-mi-sol as your tonic chord. Does it make more sense?

@Dima G Hi! Just the bit about the mixolydian scale starting on sol. Is that because it naturally starts in G?

As David Robinson said, the harmony of a particular tune is built from those scales. So knowing them and being able to sing them and hear them is extremely important in your musical development. So for a quick simple example in the key of C: The chord built on the 7th degree of the major scale is B-D-F-A which is a B min7 (b5). The chord built on the 7th degree of the Mixolydian scale is Bb-D-F-A which is a Bb7 chord. Very different harmony. Take as many ear training classes as you can so these sounds will start to live in your ears. Keep it up!

@Stephen Lacatena thanks for your reply.

I think the problem with this game and others on TG is that no examples of how they relate to actual pieces of music are provided. So, for someone like me, who has no musical education, I fail to see the connection between the scales in the Scale Spy game how they apply to the real world of music. It's like a music teacher telling me to practice my scales without ever explaining why.

Anyway, what I think you're all trying to tell me is that I need to dig deeper into all of the scales in the game., learn to play them fluently and also examine the harmony of each scale. Maybe I could seek out songs written with each scale and see how the scale and its harmony have been used to create the song?