Speech tracts lack coupling that brass instruments synchronize with.

Evidence

In speech, the vibrations in the vocal folds are not coupled to the resonances of the tracts, in contrast to many instruments, where the vibrations in the excitation are strongly coupled and synchronized to the resonances in the air column. For example, in brass instruments, such as the trumpet, the lips of the player open and close in synchrony with one of the resonances of the bore (see the simplified illustration in Figure 6. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 665

Categorization

• XREF: This contrasts the source-filter model for speech (glottal source uncoupled from tract) with instruments where excitation and resonator are strongly coupled — a distinction central to acoustic communication theory.
• QUESTION: Why did speech evolution avoid the coupling that instruments exploit? Worth chasing — an evolutionary/cognitive angle on why vocal folds don’t lock to tract resonances.