Acoustic syllable durations were measured in Estonian utterances performed in parallel as recited and sung. A systematic effect of phonological syllable length was found irrespective of the group of participants (contemporary or historic). This effect of syllable length was modified by the mode of performance: in music, it was present considerably less than in speech. In music, the effect of syllable length in turn was modified by song: it was present in two of the three songs, but absent in one song. The above results suggest that the correspondence between linguistic duration and musical rhythm in a quantity language such as Estonian is loosely defined. The nature of the correspondence between linguistic quantity and musical rhythm may be considered, to a certain extent, analogous to the tone-tune relationship in tonal languages.