One instrument can sound like two notes by weighting partials within a shared series

Evidence

It is quite possible for a single clarinet to sound like two instruments, playing two perceived notes at once—for example, a note and another note exactly a twelfth above. This is accomplished by skillful manipulation of the strength of the partials in a harmonic series, and is analogous to Tuvan singing. Such a tone is pseudo-multiphonic, since the two perceived notes share the same harmonic series. — Eric J. Heller, Why You Hear What You Hear- An…, 1703

Categorization

• DEFINE: Defines pseudo-multiphony: perceived multiple pitches arising from a shared harmonic series, as opposed to true multiphonics.
• CANDY: A single clarinet sounding like two instruments is a fun, tweetable fact about auditory perception.