One of the things that conductors have to face all the time is accompanying a soloist. It’s still a listen and react process but the technical aspects can be different, in some ways, from conducting, let’s say, a symphony.
Things to consider are balance, rests, and, of course, the musical partnership between the conductor and the soloist.
As a first thing, it’s important to arrange a private meeting with the soloist ahead of the first rehearsal. You can sing or play through the orchestral accompaniment. Note the most critical points.
Take into great consideration the soloist’s needs: a breath, the need for a bow shift, various rubatos.
Here’s video dedicated to accompanying solo instruments, the most common traps, what to look for when following a particularly fast or virtuoso piece, and the eternal question: who’s the boss?
Examples from Beethoven, Chopin, Mendelssohn.
As a conductor, you need to know every note that the soloist plays. It’s the only shield you’ll have when something unexpected happen. And, be sure of this, at some point something will happen.
Soloists will rely on you to follow their needs and you will rely on them to perform, more or less, as established over the rehearsal period. However, nobody is a machine and you need to be quick in catching a soloist who had a temporary memory problem for example. Or not jump the gun if the soloist needs an extra long breath before continuing.
It’s a delicate balance built on trust.
Balance should be your first concern: the soloist must be heard. It’s easier if you have an assistant conductor sitting in the audience to give you some feedback. But if you cannot, step yourself in the audience and let the orchestra play. You’ll see immediately if something needs to be adjusted.
Your understanding of the acoustic of the hall combined with your knowledge of orchestration will help you in making the best decisions.
A lot of the accompanying work relies on successfully restarting the orchestra after one or more rests. In a series of rests, rests before the actual preparation are marked lightly while the preparation on the last rest must be very well articulated.
If you have a few bars of rest and you do not intend to beat them, let the orchestra know ahead of time. Also let them know when you’ll start beating again: on bar 364 for example, or 1 before letter L.
What happens if, let’s say, a soloist misses an entire set of bars? This actually happened to me once with a contemporary opera: the soloist jump over an entire section skipping 20 pages in the score. As a conductor, you can be quick to jump but what about the orchestra?
You have a few options, all of them chaotic in their own way:
1 – continue to beat patterns with your right hand and signal the soloist with your left hand. Once you have contact, wait for the soloist to adjust.
2 – if you cannot establish a contact with the soloist, hold up your left hand and keep pulsing with your right hand, without patterns. The orchestra knows that something is wrong and will look for help. Call a number or a letter in a discreet way and clearly mark it with a strong downbeat. Even with both hands if necessary.
3 – stop the orchestra, call a letter making sure the soloist knows where that is, and begin again. Obviously, this is your last option.
All in all, you should put yourself in a position of being able to both hear and see the soloist. The eyes help the ears: you can see if they need to take a longer breath for example. If you’re accompanying a pianist and they have a cascade of notes in rubato, the easiest way is to listen to the bass line.
One of the most important things is, as always, breath with the soloist. It will help enormously both you and the orchestra to create a cohesive performance.