Research on the relation between sound and meaning in language has reported substantial evidence for implicit associations between articulatory–acoustic characteristics of phonemes and emotions. In the present study, we specifically tested the relation between the acoustic properties of a text and its emotional tone as perceived by readers. To this end, we asked participants to assess the emotional tone of single stanzas extracted from a large variety of poems. The selected stanzas had either an extremely high, a neutral, or an extremely low average formant dispersion. To assess the average formant dispersion per stanza, all words were phonetically transcribed and the distance between the first and second formant per vowel was calculated. Building on a long tradition of research on associations between sound frequency on the one hand and non‐acoustic concepts such as size, strength, or happiness on the other hand, we hypothesized that stanzas with an extremely high average formant dispersion would be rated lower on items referring to Potency (dominance) and higher on items referring to Activity (arousal) and Evaluation (emotional valence). The results confirmed our hypotheses for the dimensions of Potency and Evaluation, but not for the dimension of Activity. We conclude that, at least in poetic language, extreme values of acoustic features of vowels are a significant predictor for the emotional tone of a text.