Some composers put an enormous amount of detail into their notation. I see two primary trends in the last half-century (others exist, of course) that have led to this situation.
The development of electronic sound production and modification gave composers unprecedented control over every detail of a composition. For composers who place a high value on unprecedentedness, this was catnip, and fools, as well as angels, rushed in. The experience of manipulating every aspect of electronic sound led many of them to question whether the same kind of control could be exercised in acoustic music. Again, unprecedented artistic territory so, again, very attractive to many.
At this point, the novelty of hyper-controlled notation has worn off. This means that composers who were in it for the value of working in unprecedented terrain have moved on to new horizons. The composers who remain devoted to notating every twitch and tic of their music are the ones who care deeply about the shape of every moment in their compositions. As fellow composers, as fellow human beings, we shouldn’t find this puzzling – we are very close to living in a paradise where every one of us can care deeply about things that do not give many other people cause to hoot.
The other trend is the soaring cost, and declining subsidy, of orchestras, which has created a situation in which orchestral performances are rehearsed on a tight clock, and a high programming value is given to compositions that are so familiar or so comprehensively notated that they can be prepared in one or two rehearsals – in other words, repertoire for which the interpretive decisions have already been made. Unlike the first trend, this one is not creative, but economic.
Some composers, bred in the womb of current orchestral notation practices, bring the same level of notational detail to their chamber and solo works, where it is not quite so crucial. Even here, though, there are many performers who appreciate knowing that the composer knows what she wants. In fact, I’ve seen situations in which performers have asked a composer how a particular passage should be played, the composer responded, “I’d like you to decide,” and the performer responded with an unspoken, “if you don’t care, why should I?” kind of performance.
But we can all come up with anecdotes to serve our positions and preferences. The goal is to find the right fit for each of us, rather than being flummoxed by the fact that we can’t all squeeze into the same shoe.