I have many guitar friends tell me the same thing. I don't understand. If you are singing "C" how does being tuned up or down help.
I believe a "C" is a "C" no matter the tuning.
I believe SailingUke is wondering why you can't simply find chord shapes that do the job for you regardless of how the uke/guitar is tuned.
The answer is of course you can, but in that case capos would never have been invented.
Tuning down a step (e.g., from DGBE to CFAD) is is simply the inverse of, & in principle no different to, tuning up a step (i.e., from DGBE to EAC♯F♯). We'd do that if we wanted to take advantage of the 'open' chord shapes (shapes that utilise open strings, e.g., [bari] G-shape, C-shape, Em-shape, etc).
Normally however, we don't bother tuning a uke or a guitar up in pitch: we simply put a capo on the appropriate fret. Putting a capo on the 2nd fret, for example (which in standard bari tuning would give us EAC♯F♯), would enable us to play a song written in the key of A with open chords ringing out (i.e., to play it as though it were in the key of G).
I was faced with a similar situation yesterday, looking at Jan & Dean's "
School Days", a song which I thought (wrongly!) TCK was asking to have featured in his Season (it's really Chuck Berry's "
School Days", of course - and in fact TCK wanted another Jan & Dean song, too!
). Turns out Jan & Dean sing "
School Days" in the key of F♯!* Besides, F♯, the other two chords in the song are B & C♯.
Now, of course I know how to play the chords of F♯, B and C♯; but how much simpler simply to put a capo on the first fret of my uke, thus raising the pitch of my open strings one semitone, and play those chords as F, Bb & C (in other words, play the song as if it's in the key of F)?
Tuning a uke/guitar down a step is the equivalent of putting on a 'negative capo'. if you have a song that's in F, and you want to play it on your baritone ukulele, but want also to keep those open strings ringing out as you play; why
not tune the strings down a tone to CFAD, and play it as though it's in the key of G?
And as Geoff already said, if you want to use regular baritone tuning at any time, simply put a capo on the 2nd fret to get you back to DBGE.
Yes, you lose the use of the first two frets in the process, but really how many of us ever find ourselves in the dusty regions of the 12th or 14th frets?
*
Really! The only other song I know of originally in the key of F♯ is Dolly Parton's '9 to 5' - I have the sheet music!