I will try to take the mystery out of the 1,4,5 concept for you.

Here is a graphic of a piano keyboard. I am using the piano because it is visual and easy to understand.



The note shown in the middle is called "middle C. Notice there are both white keys and black. For the moment, disregard the black keys.

Starting with the C note, using only white keys, we can form something called a C scale. The letters in a C scale are C,D,E,F,G,A,B, and then it starts over. We can also number those letters. C=1,D=2,E=3,F=4,G=5,A=6,B=7. So notice that C is 1, F is 4, and G is 5. So that is where the 1,4,5 comes from.

We call that a one, four, five progression. It is the most common progression in music and thousands of songs have been constructed using that progression. There are three ways to put that in writing. One, Four, Five or 1,4,5 or I, IV, V. The last being the way you would normally see it written in musical terms.

There is a function in BIAB that lets you change the key. If you type a 1,4,5 into BIAB and tell it to change the key it will show you the letter names of any 1,4,5 in whatever key you choose.

This is one of the most basic and fundamental concepts of music theory. This idea of letters and their corresponding numbers is how we define progressions, chords, and many other things for example.

There is no absolute need to understand any of this. At the end of the day, music is about sound. If it sounds good to you, that is all that really matters. Music theory is just a way that has been developed to be able to communicate musical ideas in a somewhat standard way. Any chord progression can be used but not all chord progressions will sound good to you.

So...here are some definitions of things being discussed.

Musical scale...any graduated sequence of notes, tones, or intervals. An example is the C scale.

Chord...A chord is the layering of several tones played simultaneously. Tones are sounds produced by depressing the keys on a piano for example. An example is a C chord comprised of the first, third, and fifth notes of a C scale.

Chord Progression...In a musical composition, a chord progression is a succession of chords. An example is a one, four, five.

Key...in music theory, the key of a piece is the group of pitches, or scale, that forms the basis of a musical composition. An example is the key of C.

The deifications I have given you are the most simplistic I could come up with and there is more to learn.

I hope I have described all this in a way you can easily understand.

Billy

“Amazing! I’ll be working with Jaco Pastorius, Charlie Parker, Art Tatum, and Buddy Rich, and you’re telling me it’s not that great of a gig?
“Well…” Saint Peter, hesitated, “God’s got this girlfriend who thinks she can sing…”