When I was performing, I understood the music score to be the last word on the composer's intent and direction for playing the music. There's more to that score than meets the eye, though — and some of it isn't in the score at all.
First, there are metronome markings. Beethoven's, for example, raced sometimes, and I've heard pianists complain that they were physically impossible to perform. I've heard other pianists describe metronome markings in terms of the human heart beat while the body moves in time to the music. Running produces a fast heartbeat so Beethoven's prestissimo music runs along with the heart. While musicians agree, for the most part, that the score reflects the composer's intent, for some it's merely a starting point, including metronome or tempo markings.
Two musicians who perform together can disagree completely on the tempo, especially if the score lacks metronome markings. For example, none exist in my score of the Brahms First Piano Concerto. Instead, Brahms uses Italian descriptors — such as maestoso or adagio — to indicate tempo, at the beginning of each movement. This opens the tempos to interpretation.
Of course, there can be historically established tempos. One famous clash over tempos occurred in 1962 between Glenn Gould and conductor/pianist Leonard Bernstein when Gould performed the Brahms First Piano Concerto with the New York Philharmonic. Gould's tempos so concerned Bernstein that he addressed the audience before Gould came out to perform, as heard in the video below.
Bernstein bowed to Gould's tempos because he respected Gould's musicianship. And how does it sound with the historically established tempos?
When I began studying Mozart's piano sonatas, I approached them as I had the Beethoven piano sonatas. Wrong. My teacher explained that the piano during Mozart's time was an early pianoforte without the refinements in hammer action that the modern piano possesses, and the style of playing was different even from Beethoven.
That certainly wasn't in the score, but it affected how I played the notes, which was with a shorter, softer touch, and with pedal use forbidden. The touch and style of playing can be different for each period in music, depending on the instrument, and that won't be in a score.
Baroque ornamentation drove me crazy. Baroque composers used squiggly symbols over the ornamented notes to indicate which ornamentation to perform. How to play them is not in the score. Ornamentation symbols appear in music scores for any instrument, including voice; and from any country, most prominently from France, Germany, and Italy. I'm most familiar with piano ornamentation. Piano teachers must pass that knowledge and expertise on to their students.
Here's the ornamentation in practice.
Finally, there's the composer Gustav Mahler, who also worked as a conductor. Mahler wrote extensive notes in his scores as if he wanted to control every note of his music forever. The effect of these notes is like Mahler looking over every performer's shoulder. What pressure!
Music performance recreates what the composer wrote in the score, true — but it's more complicated than just playing the notes. There are other considerations beyond the score a performer needs to know: tempo issues, how instruments affect a score's performance, and deciphering the composer's intent from the score's written notes and symbols in addition to the music notation itself.
Cinda Yager writes essays, fiction, and two blogs in Minnesota. She loves classical music and has just published an e-book novel set in the classical music world, Perceval's Secret.