Short musical fragments consisting of a melody part and a synchronous bass part were mistuned in various ways and in various degrees. Mistuning was applied to the harmonic intervals between simultaneous tones in melody and bass (harmonic mistuning), which caused at the same time a mistuning of the melodic intervals between successive tones in the melody part (melodic mistuning of melody) and/or the bass part (melodic mistuning of bass part). The fragments were presented to musically trained subjects for judgments of the perceived quality of intonation. Results showed that the melodic mistuning of the melody parts had the largest disturbing effects on the perceived quality of intonation, followed closely by the harmonic mistuning. Melodic mistuning of the bass was less influential. It could be reasoned that the deviating interval size was probably of more importance in the perception of harmonic mistuning than the presence of beats.