Hopefully this question seems to have an obvious answer; yes, any instrument can have a variety of timbres. On the simplest level, that’s how it’s possible to tell the difference between performers on the same instrument, but how can we use this to our advantage as composers?
Case Study: the Oboe
The oboe’s range starts at a Bb3 and ends at G6, however, not all of these notes are equal.
From Bb3-E4 the oboe is loud and assertive, it’s virtually impossible for an oboist to perform these notes softly.
From E4-C6 the oboe is in it’s most comfortable range. If you imagine an oboe sound in your head there’s a good chance you’re hearing something in this range.
From C6-G6 the oboe sounds delicate and thin, but is also very difficult for the performer to control. Notes in this register can be very effective, but also tiring for the performer for extended periods of time.
The Golden Rule for composers:
Get to know the instruments and performers you’re writing for!
The same passage will sound different on different instruments and will require a different variety of technical demands. Every performer will sound different and will have different challenges when learning new music.