Bass or ground or floor levels in music, engineering

Everything in music is referenced to bass or (base) coming from the Hellenic word Βασις meaning foundation or base [Bach].


In electronic engineering usually any voltage is referenced to ground. Ground is assumed 0V. So the electric field potential at any point is really the potential difference between that point and ground.


Very similar to music.


On the song for example Save Room - Legend
https://m.youtube.com/watch?v=iOmnGzAKLvg#fauxfullscreen


Following the lyrics...


'Save (note B while bass is A)
Room
For
My
Love (note F# while bass has now changed to G)


So first great sounding interval is A to B or A B. Counting from A to B natural or white keys we have 9 keys. So the interval is a 9th. (We do not call it a 2nd, as 9ths have a very distinct particular sound atmosphere, [Piston]. It is a major ninth as B belongs to the scale A major [Piston].


The second great too sounding interval is G bass to F#. Counting again white keys it is a 7th interval. It is a major 7th interval as F# belongs to the key of G major.


In more detail the fundamental chords on which most of the song is founded are:


A C E G B


and


G B D F#


These are more or less derived by adding the 3rd [Bach], the 5th which is usually there and it is most of the time a perfect 5th (ie a note belonging to the major scale of the bass).


In the case of the first chord of the song


A C E G B


the 3rd is a minor 3rd as C is one semitone less than C# which belongs to the key of A major.


So the chord


A C E G B


is called A minor 3rd minor 7th major 9th


With similar logic:


the second chord


G B D F#


is called G major 3rd major 7th


In Bach ingenious notation both chords are just symbolized in code:


A79 and G7


Flats or sharps are automaticaly derived if one knows the key or scale of the song ie the particular set of seven notes used in making the composition (assuming key does not change in some places).


The key or scale of the particular song is A Dorian. Ie all keys white except all F which are F sharp.


Ie A B C D E F# G A


For example G7 in this case automaticaly means G B F#


And this is what sounds immediatly nice to the human brain.


References:


Bach bass rules
https://normanschmidt.net/scores/bachjs-general_bass_rules.pdf


Harmony - Piston


PS
Why does this post mention floor levels?
Bass is one note at a time but changes in time. So reference level or floor changes. When bass stays the same it is called pedal bass.
PS 2
On electron tubes used to amplify music signals etc (attention to safety as any voltage or current can be dangerous) the control grid (where the music signal is applied) quiescent potential is not referenced to ground but to cathode. (Applied Electronics - Gray - MIT)