Don't know about the rest of you, but I just started keyboard at age 62..I'm now 70.

I figured out chords on an arranger as it was similar to guitar.

For me anyway, the arranger was a way for this string(mandolin, guitar, bass, banjo player) to learn keyboard. I started one key at a time, as I did playing strings as a kid.

Thing is, keyboard/piano players don't relate to arrangers...my brother(piano player)included.

I still see the advantage of arrangers, especially as a way for folks who want to learn keyboard.