# Why have a clef change right after a previous clef?

I came across this section in Mozart's piano sonata no.

It shows a clef change at the start of the measure, but the bass clef is shown right before it. Why would this be needed if the measure uses the treble clef and does not use the bass clef?

I'm sorry if the doubt seems amateurish, but it's the first time I'm coming across such a thing.

• Is this the very beginning of the piece? If so, we have an excellent question on our hands. If not, we might still have a dupe. Commented Dec 25, 2018 at 9:58
• It isn't the very beginning of the piece of as far as I'm concerned. I'm starting to think that it could be a mistake with the uploader as the other versions didn't have this. For those concerned about the origins of the image, look up piano sonata no. 7 on Wikipedia and this is the image which pops up. I know it would be stupid to trust the genuinety of Wikipedia when it comes to sheet music and that I must look at more authentic sites, but I thought I'd ask it nonetheless as I could have been wrong in this assumption as well. Could someone please clarify for me? Commented Dec 25, 2018 at 13:17
• Does this answer your question? Two different clefs at the start of a piece on the same hand Commented Sep 11, 2023 at 15:05
• @LiamGallagher This example is not the start of the piece. Rather, it is measure 148 or so. And actually it starts on beat 2 of that measure; beat 1 is presumably at the end of the previous system. Commented Sep 11, 2023 at 20:56

So, here we have a clef change. The line before the line in question has the bottom staff in the bass clef, and in our first line here, the music begins with the treble clef. This change of clefs happens of on the first bar of the new line. So, why do we write a bass clef, only, only to have it immediately change to a treble clef? Why not just start the next line with a treble clef?

Well, the reason for this is simple: cautionary clef. We want to make the clef change obvious to someone who is sight reading. When a pianist is sight reading, he or she often do not pays attention to details, such as the clef at the beginning of the line, or the key signature. The pianist often assumes it's the same clef, and the same key signature. So if we were to suddenly put a treble clef, it might confuse the pianist who is sight reading. By continuing the line with a bass clef, and putting the treble clef immediately after it, what we are signalling is this: "here is a clef change!" in the most obvious way possible, that is, by ignoring the fact it is on the first bar of the line and treating it like any other clef change.

Of course, this is not necessary to pianists who practised the piece well in advance, they are neither benefited, nor hurt by this notation. But we want to be courteous to people who are sight reading. They need things to be really obvious.

• If I recall correctly standard practice is to indicate the clef change at the end of the previous system and then print two treble clefs (in this example) in the second system. In other words, the example in question is notated incorrectly. Commented Sep 11, 2023 at 20:40
• It's not incorrect – there are no hard rules concerning this – and if there are, these rules are a modern invention, certainly not concerning the old editions or modern editions trying to be faithful to old editions and manuscripts. While slightly unusual, it's actually quite comfortable to read. Also, note that the measure in question is incomplete, having only three beats – the first beat being on the previous line (the line break was inside the measure). Commented Sep 13, 2023 at 1:16
• It is certainly not an attempt to be faithful to any manuscript or old engraving. The first edition of this sonata has the left hand part in the upper staff, so there is no clef change at all. The other editions have the first beat of the measure between the bass clef and the treble clef, where it belongs. It's possible that this edition was created by some authority on innovative modern approaches to notation, but the more likely explanation is that it was created by someone who didn't know what they were doing. Breaking a measure like that after the first beat isn't unusual; it's unheard of. Commented Sep 13, 2023 at 2:54

It would be more usual to have a (small) cautionary treble clef at the end of the previous stave, start the new one with a normal, full-size clef.

You sometimes see it done the way shown in hand-written scores using pre-printed 'piano layout' manuscript paper.

But the example looks like it's been prepared in Sibelius. It is actually quite hard to make Sibelius notate a clef change this way! And where's the first beat of the bar? This notation would make perfect sense if there was one beat of music in bass clef starting the bar.

Perhaps noorav@ could give better details of where this was found?

• The measure in question only has three beats anyway, it's obviously an amateurish typesetting job. Splitting a measure across systems is sometimes necessary but in a Mozart sonata? Nope.
– user48353
Commented Dec 26, 2018 at 2:08
• Be nice to see the previous bar, wouldn't it?
– Tim
Commented Dec 26, 2018 at 13:31
• The deficient bar is the last bar but 7 of the first movement of Mozart's piano sonata 7 K309. In the lower stave, the first beat, and the whole of the previous bar, are in the bass clef. I wondered if the source of the image in the OP might have been a score someone created by using a program to lay the score out, and then uploaded to IMSLP. IMSLP has several such scores of various public-domain works, and in those scores produced using a program that isn't Lilypond, the layout is appalling. But IMSLP has no such scores for K309. Commented Sep 29, 2019 at 20:18