How do orchestras synchronize bow movement?

Question

The last few times I've been to see the orchestra, I've noticed that the bow movements of all the strings are synchronized. I've been in bands and choirs before but never a group with strings, so this just amazes me that there's not a single person out of sync.

I figure the three options are:

1. There's some musical standard and everyone just does it the same way.
2. It's explicitly notated in the scores from the composer, or
3. The section leaders choreograph the movement for each section.

How is this achieved?

Answer 1

All the three options you enumerate come into play:

• some bowings are obvious: a measure of four quarter notes with no markings is very likely going to be down-up-down-up. A forte note by itself will normally be a down bow.
• composers or arrangers very often explicitly notate bowings for the strings
• the section leaders will usually have the music beforehand, and they will mark the bowings in the parts for their section (possibly changing the composer's markings)
• at rehearsals the section leaders, or possibly the conductor, will often announce bowing changes
• the string players will often add markings to their part during rehearsals
• even if there has been little or no rehearsal and the parts are not properly marked, professional string players are normally experienced enough to be able to follow the leader's bowings on-the-fly

Answer 2

How is this achieved?

There is a hierarchy throughout the orchestra for each group of musicians (woodwind, brass, violinists, violists, cellists, etc.). Each group has a leader who is responsible for that section and whom the players in that section must watch. The largest group is the violinists, split into first violins and second violins. Sometimes the first and second violins play different notes to each other but quite often they play the same notes.

The conductor is the head of the orchestra hierarchy and he or she guides the musicians via their gestures. The leader of the violinists is called the concertmaster and they have several duties:

1. They are usually responsible for all the musicians tuning their instruments in the pre-concert period.
2. They usually issue bowings to the other violinists. This makes sure that all the violinists in the two sections are playing the same notes with the same bowings. Nobody is bowing a note up when everybody else is bowing down.
3. They are the leader for the violinists. This means that they watch the conductor and to this end they usually sit closest to the conductor. The other violinists have to watch the concertmaster from whom they take the lead whilst also keeping an eye on the conductor. By watching the concertmaster they know what their bow should be doing when.

Answer 3

You're missing

4. The conductor tells them what to do.

Phrasing is somewhat standardised when you learn an instrument, particularly the tendency to start bars/phrases on a down bow. The composer may have marked phrasing and slurs on the score, or the engraver may add them as guidance, so that bowing on these is explicitly stated.

The conductor (not the section leader) is the person who ultimately sets bowing though. Different bowings can sound different, most obviously for short notes at either end of the bow, so the conductor will choose bowings that create what they want "their" version of the music to sound like. Staccato notes (one note per bowing) obviously sound different too. And phrasing generally (where you change bow direction) can be set by the conductor separately from anything written on the sheet music.

Note that the leaders of their respective sections sit in front of their section. The rest of their section are able to follow them - but only the conductor can see musicians who go wrong.