While mastery of aspects of music theory is relevant to rapid learning and understanding of a new choral part, many choirs comprise members with no formal education in music theory. Also, the language of music theory is not intuitive, with many terms having meanings different from those in common use, which can present obstacles for mature learners. The authors hypothesised that students joining an internationally recognised university choir might master aspects of music theory as a by-product of rehearsals. This was tested by having new admissions to such a choir complete a music theory test at the commencement and at the end of a year. The test evaluated the ability to name and write intervals and name notes and the duration of notes. Overall results did not reject the hypothesis. Subjects with no formal music training also showed most, and statistically significant, improvement in the questions related to intervals, which are arguably the most useful skills for choristers who do not sight-read. This appears to be a new finding: the literature shows occasional references to music theory skills, but their acquisition in a learning-by-doing style is not reported. Some insights into ways of enhancing choral performance are a by-product of the principal focus of the study.