How do instruments with discrete tuning play chords alongside those with continuous tuning?

Question

I was taught that when playing a triad, the third should be played sharper and the fifth flatter than the notes would sound on an instrument tuned to equal temperament, such as the piano. However this intonation adjustment is not possible on all instruments, even though these instruments may be playing together in the same orchestra/group.

How should members of an orchestra deal with this?

• should those who can adjust intonation refrain from doing so, to avoid sounding out of tune with those who can't?
• do those who can't adjust intonation have some technique to compensate?
• is the adjustment of pitch minor enough that the different intonations are not noticeable, whilst the benefit of the adjustment is?
• do the composers/arrangers consider this limitation when assigning the parts to instruments?
• or something else?

Explanation of terms used in the title

By discrete tuning I'm referring to instruments such as the piano, where the intonation cannot be adjusted whilst playing.

By continuous tuning I mean instruments such as 'cello or trombone, where you can easily adjust the intonation of a note whilst playing (i.e. outside of tuning the instrument).

I'm aware that some instruments fall into a grey area; e.g. the trumpet has discrete tuning, but players of moderate ability can bend notes to adjust the intonation.

Answer 1

For a classical orchestra the priority is, to be in tune with your voice group e. g. first violins. A voice group consists of same instruments, so no problem, they play as you've been teached. The instruments with discrete tuning are only a few (piano, celesta, marimbaphone, xylophone, organ come to my mind) and these are unlikely to have prominent sustained notes in common with one of the continuous tuning instruments, so that this effect will seldom be noticable. Note that while your "moderate ability trumpet player" is able to adjust, this is viable for chords distributed to several voices, not for 32th sequences. So according to my experience: the musicians with continuous tuning do what they always do: they produce a tone and adjust minimally to what they hear from their own and adjacent instruments. If the result is not sufficiently reliable, for the few critical places remaining the conductor will announce, which instruments should add a sign marking "lower" or "higher" as appropriate to their sheets and that's it.

Answer 2

I was taught that when playing a triad, the third should be played sharper and the fifth flatter than the notes would normally sound.

Uh, no? "Would normally sound" is usually used to describe the equally tempered scale whereas "playing a triad" implies a tendency towards pure intervals.

A perfect major third is about 386 cents (14 cents flat from a tempered third), and a perfect fifth is about 702 cents (2 cents sharp from a tempered fifth). If you are tuning an organ, say, you lay the reference octave by first tuning a perfect fifth to the first two notes, then taking off just the bit from the upper note that leaves you with the beating appropriate for the interval.

So if you don't have the auditory skills to adjust into the "does not beat" direction, you are better off not modifying the tempered intervals at all rather than guessing.