The double stop is the most misunderstood (by orchestrators) and ignored (by players) orchestration device EVER!
I know that is a bold statement, but after many years observing the orchestra from the podium and seeing what they play and what they don’t, I can say it with assurance. Keep in mind, we are talking about writing for the orchestra here, not for soloists or chamber music. There are three things you need to think about before you decide that you need to write a double stop. The first two are related to the mechanics of playing a double stop, and the third, to the instrument itself. These are also the reasons why when you write one, they may divide it anyway.
To play a single note you put a finger down in the right place, with a ridiculously small margin of error, and bow or pluck the string. You can tune the note to it’s context and the ensemble with ease. Your hand is comfortable and it is easy rock back and forth for a nice vibrato. You have three free fingers to chose from to best play the next note. With a double stop, however, you have two fingers down. You just doubled the chances of an error. You now have two notes to worry about, tune, and vibrate.
Books are full of examples showing what double (and triple and quadruple) stops are possible, but the texts are generally considering them in isolation. You must remember that moving from a single note to a double stop, a double stop to a double stop, or double stop to a single note is much harder than moving between single notes. If you already have two fingers down, it is very hard and often impossible to make a legato transition to another double stop.
Finally, there is the resonance of the instrument to consider. Unless you are using open strings (more on that in a minute) the instrument usually resonates better playing a single note, not two of them. It can fight with itself. This is quite subtle, but is more pronounced the larger the instrument, and so still should be a consideration of whether to double stop or divide.
The problem with open strings is that players are conditioned to avoid using them. They sound brighter and more strident than fingered notes so it is hard to balance and blend them with fingered notes. If the double stop contains an open string so tuning and finger placement should not be an issue, I have found players will often still ignore it and divide.
When someone plays a double stop it does not double the volume, it only adds a little more, and due to the potential damage to the resonance and tuning it does not always increase the sound in a good way. As discussed in Divide and Conquer, in many cases you can divide sections and you will not notice any change to the mass or quality of the sound.
String players dividing notes marked as double stops is not only common in the recording studio; the concert repertoire is full of places where they will divide where the composer has not indicated they should. String players are always listening to what is going on around them and if they hear no obvious reason as to why a double stop is necessary, they will divide it, the sound will be better and that is what they care about.
Since I’ve been around a while now, if the orchestra knows I have orchestrated a cue they will play the double stops (most of the time, at least; I will admit they still ignore me sometimes) as I really mean them and have thought about it. On the other hand, when I am conducting others’ scores they will divide the notes.
You have thought about it, don’t believe me, and you want to use a double stop. How should you notate it? There are two common ways.
2: Use the bracket. The double stop only applies to the bracketed notes only, whereas the non div. text applies until there is only one note.
Don’t use both at the same time, that is redundant.
What about triple and quadruple stops? There are two considerations, and the first is the sound. These multiple stops will come out as a broken chord. The bottom one or two notes will be played slightly before the top two. This can help make a ‘stab’ wider and bigger sounding, but means the timing can be rough. Think ‘Blap’ instead of ‘Bap.’ At loud dynamics it is possible to press the bow hard enough to contact three strings at once, but it can be hit and miss, so will not be played like that in a section. It is only possible to sustain the top two notes. Secondly, you have compounded the possible pitch and technical issues mentioned above. In these cases the players don’t seem to mind playing open strings as they often have no choice. You also need to make sure it is actually playable. My teacher always told me to draw a fingerboard so you can work out where fingers are going to be. If that does not help you, check with a player or look up one of the tables that shows possible stops.
We have been told by authors and teachers to mark it when we want the section to divide and when to play unison again. But if we dictate when to divide, why then do we ever need to mark non divisi when we want a stop? The historical assumption (or in other words, the default), is that unless you label something divisi, players will perform a double stop. In reality this is not the case. Is there a default at all? I think there is, it is just the opposite of what most people think it is. The players know exactly what to do, but knowledge of that common practice hasn’t always filtered its way back to the textbook authors. They will divide unless told otherwise, and even then, they will make a judgement call as to the musical and practical sense of doing it.
I remember the first time I conducted an orchestra, I was an undergrad at the Queensland Conservatorium of music. We were playing a piece of mine and I noticed that the players were not playing double stops even in places where I had marked them. They told me they divide, it sounds better. Fast forward to working in Hollywood and one of my first jobs was as a copyist at one of the big copy houses. In the handbook for the house style it said not to use the word divisi in the parts (as they would divide anyway). I do not use the word in my scores. I use the bracket if I really want a double stop. Having orchestrated hundreds of cues and recorded all over the world with both regular session musicians and symphonic musicians playing their first session, how many times have players asked me if they should divide? NONE!
Keep in mind that we are now talking about two subjects with inconsistencies that have combined into the perfect storm of misunderstanding. Firstly, the notation of divisi and non divisi, and secondly, the practical issues of performing double stops.
So my rule and what I believe is the true default, is that for a two-way (two parts) divisi, there is no need to use the word, they will do it. Also, many times I have conducted scores where someone has missed labeling unison after a divisi, and yet I have never heard half the the section simply sit silently after the division, waiting for an indication to play again. To me, that indication is completely redundant. But I know I am bucking hundreds of years of tradition with this so I do not get too upset when I see others use the word.
Therefore in 95% of musical situations, I recommend never writing double stops. So what are the 5% where I do use them?
1. Clusters: As there is already dissonance in a cluster, the potential tuning issues of double stops are not a problem, in fact it is an advantage. We can get a lot more notes, in a way that can be sight read. To make it even more crunchy, pick an interval that is not easy to play and tune.
2. Big resonant chords in C,G, D and A: This is where theopen strings can be used to great advantage.