Purpose: Models of speech production often abstract away from shared physiology in pitch control and lingual articulation, positing independent control of tone and vowel units. We assess the validity of this assumption in Mandarin Chinese by evaluating the stability of lingual articulation for vowels across variation in tone. Method: Electromagnetic articulography was used to track flesh points on the tongue (tip, body, dorsum), lips, and jaw while native Mandarin speakers (n = 6) produced 3 vowels, /p a /, /p i /, /p u /, combined with 4 Mandarin tones: T1 "high," T2 "rising," T3 "low," and T4 "falling." Results: Consistent with physiological expectations, tones that begin low, T2 and T3, conditioned a lower position of the tongue body for the vowel /a/. For the vowel /i/, we found the opposite effect, whereby tones that begin low, T2 and T3, conditioned a higher tongue body position. Conclusions: The physiology of pitch control exerts systematic variation on the lingual articulation of /a/ across tones. The effects of tone on /i/ articulation are in the opposite direction predicted by physiological considerations. Physiologically arbitrary variation of the type observed for /i/ challenges the assumption that phonetic patterns can be determined by independent control of tone (source) and vowel (filter) production units. [Paper presented at the International Seminar on Speech Production (ISSP) (10th, Cologne, Germany, May 5-8, 2014).]