There's a little bromide that used to be very popular on wedding programs, that, like most really popular bits of sentiment, didn't sit well with me. It was meant to be really nice, of course:
Don't lead me, I may not follow
Don't follow me, I may not lead
Just walk beside me and be my friend
Which sounds simple and lovely, but doesn't really work in a marriage or anywhere else. There are times when you have to lead the other person, times when the other person leads you, and yes, times when you both walk leisurely into the sunset together holding hands and everything works out nicely.
I bring this up because I think accompaniment works the same way.
First of all, the chairman of the department of said accompanying in college hated the word. She preferred to call it "collaboration." That does sound like a more equal term in some ways, but it still needs to be understood correctly.
There were folks who joined the "collaborative piano" department because they were too shy to be soloists, much the way violists are sometimes people who don't play the violin well enough or lack confidence. That doesn't really work in either case.
That's because a collaborator has to have the boldness of a soloist, mixed with the discretion of a respectful partner. In other words, you've got to have the ability to take charge and the wisdom to know when that's necessary.
There are some places, of course, when the choir stops singing, or the instrumentalist stops playing, and you have an interlude all to yourself. Some of the wallflower accompanists in college would get nervous and make a mess of passages like that because suddenly they didn't have the security of someone else playing along.
You could be an organist playing an introduction to a hymn or a pianist playing a violin sonata in which the piano plays the opening measures alone. Either way, you have to set the tempo, you have to set the mood, and you have to deal with the fact that people are listening to you alone, and that any mistake in the piano part is going to be noticeable. But then, that's usually true of my situation anyway. Even when I'm collaborating with the 70 voice choir, I figure that if a false piano note develops, it will be obvious who did it. No hiding behind 5 other tenors!
You've got to have the guts to be wrong in order to be right. You can't wait for somebody else to start the piece, or hide behind their sound. In fact, you often have to be ready to equal or even outplay your choir or soloist.
Heresy! they all cry. An accompanist should always be softer than the soloist or choir. That's why they are an accompanist.
Not true. There is also a line, a chord, something that is an important part of the music that needs to be heard. It may be a small percentage of the notes on the page. It usually is. But one of my most important jobs is to recognize those places. It may be that the composer has given the piano alone a chord on the downbeat of the measure and the entire choir comes in on beat two. In that case, that chord has to be the equal in volume to the whole choir or it will sound musically wrong, and it needs to have sufficient vigor to give the choir a secure sense of the rhythm, so they can bounce off of the beat that they don't get to sing.
Changes in harmony that are given to the piano, or to the rhythmic inflection--if the musical information is not in the solo part, than it must be audible. The clarity of the musical argument depends on it.
And if it is redundant--if the soloist or choir is already giving out the information (i.e., singing the same notes)--I back way down or leave those notes out altogether, to let my partners shine out. Unless they turn out to need help, of course, in which case I offer as little as is needed to help them achieve their independence!
One of the best compliments I've received is from the choir members who have said "you make us sound better" because I think it illustrates what I hope is true about my approach to accompaniment. To be solid and secure and to let your choir or soloist shine forth when they are in fine form, giving them strategic help when they are not, and, without drowning them, serving the music such that the important notes come through clearly no matter who has them.
I sometimes hear that the problem with other accompanists is that they think they are soloists. Now here's where it gets tricky. I've been talking about accompanists as if being soloists is a useful skill. I still think so. The problem is in what kind of soloist we are talking about. A good soloist to me is one who listens. Even when playing by yourself, you have to balance the different parts of the music and be sensitive to the musical material, bringing some things up and some down. Often what emerges with persons who cannot accompany well is that they really don't listen very well. Because the only real difference between balancing a solo sonata and playing in an ensemble is that some of the parts that you are listening to, you aren't initiating yourself. But if you are used to listening, to liberating music from your own physical motion, it doesn't really matter. It is just as important or unimportant regardless of where it is coming from. Besides, even in a solo piece, there are often places where the soloist is playing an accompanying figure, as in several piano concertos. A soloist can never escape the need to be a collaborator any more than a person can live completely apart from society. And an accompanist can't avoid being a soloist, either.
But then, I do plenty of both kinds of playing, so I guess I would think that way, wouldn't I?