I’m not a musician and cannot read music. I recently started listening to classical violin pieces and noticed that there innumerable penciled notations throughout the score. Why isn’t the original sheet music clear ? Are the violinist essentially rewriting s variation?
If the composer was alive could he/she include the descriptions to avoid deviation from the intended “sound”?
I’m not a violinist, I’m a choral vocalist. If you rummaged through my box of pieces our choir has done in the past, you’d encounter notations and scribbles on at least 50% of the pages.
“AIR” --> experience shows me that the next long phrase requires more of it so inhale some
“5 ^” --> I’m a mediocre reader of music and right at the page turn (or where the music wraps to the next line on the same page) the interval throws me off, so I’ve specifically marked that it hops up a fifth
“{dark emphasized crescendo marks}” --> the choir director wants us to really swell louder here
"{scribbled through the tenor line at the top of page 12 where the only vocal parts are soprano, alto, and tenor} --> there’s no freaking bass part on this line; yeah usually the bottom-most line is the bass line but don’t sing that, it ain’t yours
If I were a violinist they’d be very different markups; violinists have different concerns and experiences than choral vocalists. But most of them will be either instructions from the musician to her SELF or else instructions from the conductor or director.
I keep playing a note wrong.
My interpretation of the notation (if there is any) differs from what the conductor wants.
Bowing directions.
Fingering
Cues from other instruments
Anything to help me not fuck up something I fucked up. We start rehearsing Monday for a concert Friday, so it’s not like I have the piece mastered.
Many earlier works were published with minimal dynamics notation. So yes, the composer could have been more clear. But often they weren’t.
I’m not a violinist, but I did grow up learning classical piano, so I do read sheet music. Sheet music only tells you so much. There are many ways of interpreting the same sheet music (some subtle, some not so subtle.) That’s why people have preferred performances of classical pieces: no two orchestras or quartets or soloists, etc., play them exactly alike.
Without seeing the notations, we can only guess. For me, my notations for piano scores would be notes to myself regarding fingering, or to avoid rushing or slowing down a section, or to bring out certain notes in one of the hands, or remarks about phrasing, etc. Basically, just notes to myself as a performer to remind myself how to express certain passages.
Would you by any chance have a screenshot or photograph of the score that you can share so we can see what these notations are?
I’m also a choral singer, and I make lots and lots of notations on my music. Notes to myself about where to take a breath, where to cut off a note, how loud/soft, fast/slow. I even have a trick when there’s a page-turn, I’ll write in the note that’s at the top of the next page at the end of the staff on the previous page. Our choir director will go so far as to say, when she’s handing out new music, “Here are some with alto/tenor/etc. markings,” so you can profit by earlier singers’ notes (if you can decipher them). ALWAYS IN PENCIL.
This is an interesting question. Some performers/conductors feel you should strive mightily to perform the piece as intended by the composer, but others favor interpretation, and that can change over the years (centuries, if applicable).
A good example of this is Handel’s Messiah, a piece I love. At one time, I owned 12 recordings of it. When I was growing up in the 50s-60s, giant choirs performed this with BIG orchestras. Then in MY 50s I attended an exquisite performance with only 16 voices (4 in each section) and a small ensemble–this was thought to be more authentic. To wit:
I hope more musicians will chime in 
with opinions about interpretation and following the composer’s intentions.
Violinist/violist/cellist here. My guess is that most of the notations involve bowing and fingering. These are things that are not always indicated in the score.
As has been said above : fingerings, bowings, where to let the music breathe, where to “push it forward”, solutions for tricky bits, interpretative ideas (dynamics, contrasts, tempo relative to other passages).
You can often find sheet music of the same piece with of without fingerings. As a beginner, it is usually a good idea to have an edition with fingerings in order not to become stuck in dead-ends (I’m supposed to play this but the way my hands are positioned now makes it awkward/impossible. I can’t think of a better way to play it, though). It is however important to be able to learn how to do without. This is where a teacher can provide invaluable insight. Countless times, I found my self stuck because the fingering I had devised worked only for the “current” notes but made a poor starting point for the ones that followed. My teacher would then say : “Why don’t you try this ?” and it worked.
Plus as has been said, it’s a way of remembering great ideas that you might forget if you stop playing a particular piece for months.
Here’s the problem. If you don’t read music, you may not be aware that music notation does not encompass everything about how to play a piece as would be ideal. Besides, individual players have individual quirks, and often want to remind themselves of something others don’t need, that was omitted in the original, or to correct a notational error.
Ever see a scribbled “glasses” doodle? That means “look sharp, or you might miss something and fuck up!”
I don’t know how to link to the image but Yehudi Menuhin’s markings are insane.
Here’s one. I see things like bow markings, fingerings, notes on vibrato, circled passage, etc.
…and quite a few phrase markings (arcs), including phrases within phrases.
If it’s a boring musical score, then the musicians may be adding more sax and violins.
I play a whole bunch of wind instruments, but I’ve only got paid cash money for playing the tuba.
My markings are limited to “breathe,” “BLOW,” “breathe,” “BLOW.”
Think of it this way—the composer’s score indicates what sound you’re supposed to produce, but it doesn’t tell you how exactly you’re going to do it.
And the notes are going to go by pretty fast, so you’re not going to have time to solve problems from scratch each time.
So yes mostly bowings and fingerings. (Once you get more than two ledger lines above the staff, I’m not seeing the notes any more, so I would need hints.)
Some reminders of flats, sharps, naturals. Some extra rehearsal numbers so everyone knows where to start. Sometimes early page turn indications. Some help counting rests or cues from other instruments.
And if you screw something up in rehearsal you make a note of it s a reminder.
And notation only gets you so far. Conductors actually make decisions on how exactly to implement the notations, so there will be reminders of those choices too.
The elliptical cylinder with the dot at the bottom indicates “More cowbell.”
d&r
I sang in a church choir for years. I left it, owing to moving out of town, but I still have my hymnbook from those days. It is full of pencilled notes indicating what our choirmaster wanted us to do with each hymn.
As others have noted (excuse the pun), there can be any number of reasons why a musician might write something on the sheet music.
Piano player here - notes include hints for notes that go way above or way before the staff lines (I actually do need a full size keyboards for some things I play and I’m not afraid to go to the edges), reminders of fingerings as Les Espaces Du Sommeil mentioned, in some cases my hands aren’t physically large enough to make the original chord as written so I modify it (Scott Joplin must have had hands at least half again as large as mine), and so on.
Doesn’t matter what you play (including your own vocal cords), at a certain point you start making notes. Reading music isn’t exactly like reading a book, it’s more a set of instructions to assemble a performance.