The purpose of this study was to examine the effects of timbral instructions on pitch and timbre production. High school (n = 28) and collegiate (n = 28) trumpeters played sustained tones at two octave levels (written C4 and C5) following three types of timbral instructions (dark-timbre, bright-timbre, or neutral instructions). Presentation orders were randomly assigned. Dependent variables included one acoustical measure of pitch (absolute cent deviation) and one acoustical measure of timbre (spectral centroid). Participants also reported which type of instruction they perceived to result in their "best sound" and their "most in-tune performance." Results indicated a significant interaction between timbral instruction condition and octave. Post hoc testing revealed that timbral instructions affected participants' absolute cent deviation, but different effects were observed in each octave. The effect of timbral instructions on participants' spectral centroid was nonsignificant. Participants demonstrated a preference for the neutral instruction over the dark- and bright-timbre instructions, and their tuning accuracy varied by octave and instruction condition. These data suggest that music educators may need to use timbral instructions judiciously so that the instruction to play with a different timbre does not result in unintentional changes in pitch.