@Elio At first I wondered how you could be responding if my response was already gone.
Then I figured I must have deleted
while you were actually typing.
But what are the chances of that happening twice?
Anyway, why did I delete.
I find these types of discussions frustrating. I was responding to "knowing the key is "
easier".
The OP asks if the circle is an "acceptable tool for reference".
My question is "for who (whom?)?"
Things are easier and useful for people they are easier and useful for.
"Experienced" musicians know Keys and relationships.
Novice musicians need to go through some kind of initial process or have reference tools or learn "tricks" or short-cuts before things become second nature and they don't need to go through some kind of initial process or have reference tools or learn "tricks" or short-cuts anymore.
If I say I have a song and say it's in the key of Bb minor (Paleo's Song in Bb minor), some musicians will know which notes will have #'s in the melody and chords and some will have to stop and figure out what the scale is and where the sharps will be.
Some will know a pattern on the guitar and know all the notes will be in that pattern even if they don't know what they actually are.
If I notate the song in standard notation without a key signature, I will have to write in all the #'s myself.
If I notate it with all natural notes without a key signature, some readers will have to go through and put all the sharps in.
If I say it's in Bb minor
and provide a key signature everyone should know where to add the #'s.
Even then, some may to go through the song and write in the #'s themselves.
Just as some need to go through a song and write in the count.
To me, all these discussions just come down to how experienced someone is.
Again, I feel like I'm just rambling and going around in circles (5ths or otherwise), so I think I take a break for awhile.
My only hope, as always, is that I'm being helpful in some way.
Otherwise I would just keep my mouth shut.
(Which would make some members happy.)