We recently got an excellent music theory-related question from a student which reflected a misunderstanding of terms that confuse many students and wanted to share it with everyone (because as we all know, if one student has a question, others do, too!)
[From the student]: I noticed the [theory] course does not cover any understanding on left-hand bass accompaniment with modes. I struggle daily trying to practice because I do not know what bass note goes with what mode. For example, how would I know which bass notes to play in a 1-7-3-6-2-5-1 progression? So far, all I have heard is play the 3rd or the 5th. Do you have any other courses explaining this type of bass note accompaniment or theory?
Students get understandably confused when we talk about modes, degrees of the scale, Roman numeral analysis (ie, harmonic progressions), and chord tones. Here, we will try to put all of that confusion to rest.
Modes = scales. "Modes of the major scale" refers to the 7 different modes/scales that we can create by starting a scale on each note of the major scale. Having 7 notes of a major scale means we have 7 modes that can be created from a major scale. (Ex: The notes of a C major scale = C, D, E, F, G, A, B. If we start a scale on C and play the notes C, D, E, F, G, A, B, C, we get a "C Ionian scale." If we start a scale on D and play the notes D, E, F, G, A, B, C, D, we get a "D Dorian scale." If we start a scale on E and play the notes E, F, G, A, B, C, D, E, we get an "E Phrygian scale." And so on.
Degrees of the scale = the individual notes that make up a scale in the order in which they appear when playing the notes of the scale in ascending order. Take an F major scale and play the notes in ascending order = F, G, A, Bb, C, D, E, F. The first note you play ("F") is the "1st degree of the scale." The fourth note you play ("Bb") is the "4th degree of the scale." And so on.
Roman numeral analysis = the Roman numerals musicians use to communicate harmonic progressions. "Harmonic progressions" is just a fancy way of saying "the order in which the chords happen." So if I said something like "the harmonic progression is I, vi, ii, V in the key of E major," that would be translated as "the chords are E major, C# minor, F# minor, and B major." Notice the similarity between Roman numerals and scale degrees. Both indicate a note's order of appearance in the scale, but scale degrees refer to a particular NOTE in the scale; Roman numerals refer to a particular CHORD that is built on that scale degree. Remember also that scale degrees are spelled with a regular number (ie, "5th" degree of the scale), and Roman numerals use upper-case if major/dominant, lower-case if minor/diminished (ie, the "V" chord in the key of C is a G major chord. The "ii" chord in the key of A major is a B minor chord).
Chord tones = particular notes of a chord. And those particular notes are the root (or 1st scale degree), the 3rd, and the 5th. If the chord is a 7th chord, the 7th scale degree is also a chord tone.
Let's get back to the student’s question. "Bass notes" can refer to anything you choose to play in the bass register (ie, left hand) and doesn't specifically refer to any mode or scale. When asking "which bass notes to play in a 1-7-3-6-2-5-1 progression," I see a couple issues that I need to correct. I would first need to know in which key we are playing in order to answer this question. Secondly, the progression (even though I know exactly what the student means) is technically incorrect because he used regular numbers (which refer to scale degrees) and should have used Roman numerals (which refer to chords).
So let's plug in some information. If we are in the key of G major, which has a key signature of 1 sharp (F#), then I would answer by saying "the bass notes of a I-vii-iii-vi-ii-V-I progression in the key of G major would be G, F#, B, E, A, D, G." Are you able to see what I did there? First, I referred to a specific key (G major) because otherwise the harmonic progression has no context. Scale degrees and Roman numerals must refer to a specific key, otherwise they are merely a formula that could apply to any key. Secondly, I changed the regular numbers to Roman numerals because I know what’s really being asked is "what are the bass notes that would correspond to these CHORDS." One other little thing I did was to use upper-case or lower-case Roman numerals depending on whether the chord indicated is a major or minor/diminished chord.
Now, one last piece of information to bring this all full circle. What are the CHORDS in the above progression? Answer = The chords in a I-vii-iii-vi-ii-V-I progression in the key of G major are: G major, F# diminished, B minor, E minor, A minor, D major, G major. Now maybe what the student was trying to ask is “What are the modes that correspond with these chords?” Ahhh, well that’s a question that introduces a new term - chord scales.
- are scales which contain the notes necessary for creating a particular chord and, in the jazz world especially, improvising over that chord. If I encounter an A minor chord and want to improvise over that chord, I might first want to know which scale would work over A minor. The answer will be a chord scale which contains all of the notes that make up an A minor chord (i.e., the chord tones of A minor) and also fits into the key in which I’m playing. So, if I’m playing in the key of G major and I encounter an A minor chord, I want to find a scale that has all of the chord tones of A minor and fits in the key of G major (i.e., does not use notes outside of the G major key signature). The answer would be a scale which uses the following notes - A, B, C, D, E, F#, G, A. But what is this chord scale called? An “A dorian scale.”
Here’s a little twist on that question. What if I encounter an A minor chord while playing in the key of F major? What chord scale should I use to improvise over A minor in this instance? The answer is a chord scale that uses the notes A, Bb, C, D, E, F, G, A - all of the notes of an A minor chord, and also only notes contained in the key of F major. What chord scale is this? It’s an “A phrygian scale.” I hope you’re starting to understand this relationship between chord scales and modes. It’s certainly a little confusing at first, but actually somewhat easy once you get all the music lingo straight.
As always, happy practicing!