Harmonic Spectrum of String Instruments
String instruments in particular have a very rich harmonic spectrum meaning that besides their “played” pitch, a whole set of harmonics will sound quite prominently as well. This applies particularly for the next few harmonics being an octave, an octave and a fifth and two octaves above the sounding pitch. The higher ones are sounding as well but get gradually softer the higher you go. This rich harmonic spectrum is part of the reason why the string section in itself often sounds so massively homogenous that it is often very hard to distinguish individual lines. For composers and orchestrators this property is relevant when voicing chords. There are two essential things to consider: 1.) octaves keep reinforcing themselves. If you have string lines in octaves the harmonics of the lower octave will reinforce the sound of the higher octave which in general will give you a more substantial sound. This also means having a chord where the highest violin note (possibly in small numbers (e.g. due to divisi or simply small line-up)) is not doubled an octave lower, there might be a tendency of this note becoming thin and shrill. 2.) Which is applied quite often in other contexts as well but works particularly well with strings: leaving out the fifth of the chord in the voicing. If you for instance need to have a 5-part chord sounding in a string quartet and you don’t want to use any double stops, an easy strategy is to leave the fifth of the chord out and plan it in as a “ghost note” from the fundamental. If your cello plays the the fundamental of the chord, you can count in the fact that there will be a quite strong sound of the fifth an octave+fifth above that sounding fundamental. On stronger dynamics you might even consider applying this technique in spite of having enough voices available as a chord with an actually written in fifth might sound too thick and compact. This whole strategy can be extended really far beyond the things just mentioned. Considering the fact that low fundamentals on strings provide basically already a major triad in their harmonics, the way of balancing chords in strings can become really very detailled. The essence should be that you always take the first few harmonics of each (relatively low) note in your string writing into account when balancing. (High notes are not as relevant as their harmonics will be more likely in such a high frequency range that they don’t have much influence on the overall sound). On another note: this of course does not only apply for string instruments but any other instrument as well, however it is particularly relevant on strings.