The aim of this study is to try to investigate the spatial-temporal reasoning states of primary school children between the ages 8 and 11 who play an instrument, regarding mathematics lessons from the teachers' views. This current study is both qualitative and quantitative in nature. In other words, the mixed research method was used in the study. Regarding the teachers' views, the memories of these students in mathematics and music lessons were found to be "excellent". Also, their effective use of numbers and visual intelligence in music lessons was found to be "excellent". As a result, it was seen that there was a significant but weak correlation between the spatial-temporal reasoning states of children who played an instrument, regarding the mathematics lesson, and the abilities of playing an instrument.