Problematic Woodwind Unisons
Intonation on woodwind instruments is sometimes quite trickier and way more problematic than samples might make you believe. There are few configurations where slight intonation differences become very obvious:
1. Avoid exposed unisons on Oboes. The very strong harmonic spectrum of the sound of the Oboe makes intonation differences very obvious and where two Oboes play an otherwise solistic line together, it’s almost impossible to get this properly in tune. In a busy tutti where the two Oboes just add to the overall sound, this problem is not much of an issue, though.
2. Avoid doubling Clarinets in octaves. Due to the construction of the Clarinet, it is unable to produce even numbered harmonics in its sound. So the first harmonic over the fundamental tone is not (as expected) the octave but the octave+5th. This makes a lot of what defines the typically transparent sound of a Clarinet. The higher harmonics are not as stable and generally “where they should be” as one would expect so doubling Clarinets in octaves (which would mean to fill up the missing harmonics) creates very often a problematic tuning impression, even though the fundamental notes are intonated properly.
3. Some composers/orchestrators extend the problem of the Oboes to the similarly double reeded Bassoons but this seems to be more a matter of taste. The bottom line here is: be cautious when orchestrating for Woodwinds and make conscious decisions. Be aware that intonation is by far not just “pressing a key”. There are exceptions to all of the points above in the literature, even on very successful pieces, so use these as guidelines, not as rules written in stone.