Research has shown that people inaccurately assess their own abilities on self-report measures, including academic, athletic, and music ability. Evidence suggests this is also true for singing, with individuals either overestimating or underestimating their level of singing competency. In this paper, we present the Melbourne Singing Tool Questionnaire (MST-Q), a brief 16-item measure exploring people's self-perceptions of singing ability and engagement with singing. Using a large sample of Australian twins (n = 996), we identified three latent factors underlying MST-Q items and examined whether these factors were related to an objective phenotypic measure of singing ability. The three factors were identified as Personal Engagement, Social Engagement, and Self-Evaluation. All factors were positively associated with objective singing performance, with the Self-Evaluation factor yielding the strongest correlation (r = 0.66). Both the Self-Evaluation factor and a single self-report item of singing ability shared the same predictive strength. Contrary to expectations, our findings suggest that self-evaluation strongly predicts singing ability, and this self-evaluation is of higher predictive value than self-reported engagement with music and singing.