This seems to be the big question in the online forums these days. Do you need them, what do you need? You’ll hear some players cry that the end of jazz was when they began teaching chord scales. Chord scales are exactly what the name suggests. Chords built from scales for example the Harmonized Major Scale. It’s actually correct name is The Harmonized Major Chord Scale. So, that’s a bit of a head scratcher to me….
Anyway, to answer the original question from the beginning of this post the short answer is, it depends. The basic scales, major, and the 3 minors (melodic, harmonic and natural) are absolutes. Yes, you need them. You could also throw pentatonics there.
What kind of music are you playing? If you’re playing straight ahead jazz. Standards and such. You can absolutely get by without ever learning modes. In fact your time would be better spent learning arpeggios, enclosures, and not even bothering with modes. If you plan on stretching the harmony of the songs then modes begin to become useful. Not a necessity, but useful.
If you’re playing modal music, then you need to understand modes and how to use them. Modal music has its own way of creating tension and release. However, to really understand and hear it you need to develop your understanding of cyclical harmony and its resolutions.
It also comes down to how your brain works, how you are most comfortable learning and absorbing information. For some, that means keeping things simple. For others that means really getting into the weeds and the minutiae of how things work. For example someone who needs an organized name for every sound might be better served by learning modes. If it helps to organize everything into small packages to create more useable tools (sounds) for you, then go for it. If getting that deep obfuscates things for you, then keep it simple.
I get asked quite often how I learned. I think I started like most. Learning the basic scales and using them until the sounds they produced didn’t quite do it for me anymore. I also had a very, very solid foundation in constructing chords, using substitutions, all of the typical things you find in jazz and popular harmony. When I started improvising I began using the “key of” approach. Relating the chord progression of a song (or a group of substitutions) to the key it is in. This served me for a while when I was getting my standards playing together. So we’re talking major, the 3 minors and the whole tone scale. Also, arpeggios. It took time to get it to a point where I didn’t sound like I was simply playing chord to chord and actually began creating melodies that made harmonic sense. It also drilled into my playing how to deal with the harmonies at a basic level.
When I began to play songs containing more altered harmonies I realized I needed to at the very least understand certain modes. By understand I mean learning what notes they gave me in relation to the harmonies I was dealing with at the time. However, I never studied them to be able to run through a scale. I studied them to learn WHERE ON THE FRETBOARD those notes were in relation to the chord they worked for. I made sure that I could find a voicing of the chord they worked with every place I could find the scale. Sometimes people call this approach the cages system, trust me it’s not. I’m talking about turning the entire fretboard into whatever sound you need it to be. I did have to practice those scales/modes in order to be able to actually play those notes. There’s no way around it.
Of course there were also other things I studied. To go through all of that in this post would be much more writing than I’m willing to do right now and also detract from the point of this post. Eventually, where I ended up is not thinking in terms of scales at all when I improvise. That doesn’t mean I just mindlessly play anything. It just means I know where the sounds I want are now, so I simply play what I’m hearing, most of the time. Which hopefully is everyone’s goal.
We all want I play music at a high level. I’m sure you’ve heard players talk about being in the zone. I think we’ve all had that experience. For myself the feeling is as though I’m just a witness to what’s happening. The notes come out and if I can keep out my own way, I can do no wrong. Those times are brought about when your mind, body and ears are 100% on. You’re running on all cylinders and just letting it happen. Meaning, all that hard work is paying off.
Getting back to my original topic of what you need. You need whatever it takes for YOU to be able to create music with sounds that YOU hear. Anything and everything you learn that can help get you there is a worthwhile pursuit. You’ll know immediately if it makes sense you. This also comes back to who you study with, if anyone. You should never leave a lesson not understanding the concepts that were covered. After spending over 30 yrs teaching I can tell you there are two reasons for that to happen. Either it was a lesson you weren’t ready for, or that particular teacher doesn’t really understand it either and wasn’t able to explain it (in which case you should take that as a clue to find another).
So when it comes down to what you need to know. In short the answer is a firm, It depends on where you want to take your playing.