> Why have a bass and treble cleft be different?

There are actually even more clefs than just those two, but those two are by far the most common. A while back I was curious why guitar music is written transposed up an octave and why it is written on the treble clef instead of using both bass and treble clefs like piano music.

One of the thing I found when searching for the answer to that is that piano music is written using two clefs at least partly because the hands are largely independent on piano so it can essentially function as two instruments. Music that for strings might take two instruments to play, such as cello and a violin, can be played on one piano with one handed taking the part for the bass instrument and one taking the part for the treble instrument.

It thus makes some sense to notate the left hand part with the same clef common for bass instruments and the right hand part with the same clef common for treble instruments.

The answer I found for why guitar uses just one clef and why it is transposed is that (1) using the transposed treble clef was cheaper and faster back in the days when printing music was expensive and hard, (2) guitar doesn't have the hand independence piano does.

Here's where guitar in EADGBE tuning would fit without transposition on the piano bass/treble clefs, on just the bass clef, and on just the treble clef:

Actual Actual Actual
Grand Bass Treble

--E- --E- --E-
D D D
--C- --C- --C-
B B B
--A- --A- --A-
G G G
---------F- --F- ---------F-
| E 12 E 12 | E 12
---------D- --D- ---------D-
| C C | C
---------B- --B- ---------B-
| A A | A
---------G- --G- ---------G-
| F F | F
---1st---E- 1st --E- ---1st---E-
D D D
middle --C- middle --C- middle --C-
2nd B 2nd B 2nd B
---------A- ---------A- --A-
| 3rd G | 3rd G 3rd G
---------F- ---------F- --F-
| E | E E
---4th---D- ---4th---D- 4th --D-
| C | C C
---------B- ---------B- --B-
| 5th A | 5th A 5th A
---------G- ---------G- --G-
F F F
6th --E- 6th --E- 6th --E-

The 1st, 2nd, 3rd etc mark the notes on the open strings. I've also marked middle C for reference. The 12 to the left of the second highest E marks the E on the 12th fret of the first string, which is the highest fret before the neck joins the body on a normal classical guitar. The fretboard has frets beyond that, but unless the guitar has a cutaway body they are harder to play so aren't used as much. Classic guitars usually have another 7 frets beyond that which would go up 4 more notes to B. Acoustic guitars often have the neck join the body a little later and have one more total frets so go up to the C above the 12th. Electric guitars typically have the neck join the body way higher and have 12 frets above the 12th fret, going all the way to the E an octave above the 12th fret.

Still, most guitar music is going to mostly stay below that 12th fret. Given that, it fits pretty well on the piano style bass/treble clefs. If music had been cheap and easy to print, and we didn't get hung up on the guitar not having the hand independence of the piano, I think notating guitar without transposition on the bass/treble clefs like piano would have worked out fine.

If that's too hard and expensive, then it becomes clear why it gets transposed. If it was notated just using bass clef you'd need ledger lines for everything on the top two strings, which is often most or all of your melody. When your printed music involves hand typesetting on primitive equipment that is annoying.

Even worse would by untransposed on the treble clef. Now almost everything played on strings 3-6, and much of string 2, would need ledger lines.

Transposing up an octave gives this:

Transposed Transposed
Treble Bass

E E
--D- --D-
C C
--B- --B-
A A
--G- --G-
F F
--E- 12 --E- 12
D D
--C- --C-
B B
--A- --A-
G G
---------F- -F-
| 1st E 1st E
---------D- -D-
| middle C middle C
---2nd---B- 2nd -B-
| A A
---3rd---G- 3rd. -G-
| F F
---------E- -E-
4th D 4th D
--C- --C-
B B
5th --A- ---5th---A-
G | G
--F- ---------F-
6th E | 6th E
-----------
|
-----------
|
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Transposed up an octave on the treble clef needs the same number of ledger lines to cover from the lowest note on the 6th string up to the 12th fret on the 1st string as does untransposed on the bass clef, but it it puts the bulk of more music in or next to the lines of the staff so there will usually be fewer times you actually need to use ledger lines.