Despite the importance of feedback in musical performance education, there is a lack of quantitative and cross-instrumental examination on what feedback is effective for students. This study collected recordings of performances by students on three instruments (oboe, piano, and guitar) and gathered written feedback from multiple teachers for each performance. Quantitative analysis revealed that the usefulness of feedback varied significantly among teachers, independent of musical instruments, compared to pieces or students. We then conducted multilevel modeling based on hierarchy among teachers for each instrumentx and found that the number of sentences giving objective information significantly contributed to the usefulness of feedback. Our findings have high generalizability and can be applicable to face-to-face lessons. The collected recordings and written feedback have been published, and can provide valuable resources for music educators seeking to improve their teaching practices.