Peer tutoring is one of the peer-assisted strategies that enhance both teaching and learning through reciprocal interaction (Johnson & Johnson, 1991; Topping, 2020). Prior research suggests that pre-training in skills such as sequencing instruction, providing feedback, and transferring knowledge improves the effectiveness of peer tutoring (Duke, 2005; Fernández-Barros et al., 2023; Liu & Saccardi, 2025). However, limited research evidence exists on the role of training duration in collegiate group piano contexts, particularly with a powered sample size. To address this gap, the present study examined how training duration (two-day vs. four-day) in different piano class levels (Group Piano II vs. Group Piano IV) influenced undergraduate non-keyboard music majors’ achievement in harmonization and transposition, as well as their learning attitudes toward piano learning. Participants were 112 students enrolled in four sections each of Group Piano II and IV at a large Southern U.S. university in Spring 2025. Using a 2 x 2 factorial design, students received structured peer tutoring training in sequencing (two-day condition) or sequencing plus feedback (four-day condition) before engaging in eight weeks of peer tutoring. Performances on harmonization and transposition tasks were assessed pre- and post-instruction, scored for right-hand accuracy, left-hand accuracy, and continuity. Inter-rater reliability was established, and two factorial ANOVAs tested main and interaction effects. Students also provided qualitative reflections on their peer tutoring experiences. Results showed a robust main effect of training duration, that students in the four-day condition scored significantly higher than those in the two-day condition in both harmonization (F(1, 85) = 44.48, p < .001, η² = .344) and transposition (F(1, 85) = 47.69, p < .001, η² = .359). Group Piano IV students scored higher than Group Piano II students on harmonization, but no difference between levels emerged for transposition. Importantly, the benefit of extended training was consistent across both levels with no significant interaction effects. Thematic analysis of open-ended responses indicated that peer tutoring training and interaction sessions enhanced students’ confidence, self-reflection, and receptivity toward piano learning. These findings extend peer tutoring research by demonstrating that even giving students just a little more training can clearly improve both their piano skills and their attitudes toward learning. For music educators, the results provide evidence-based guidance for structuring peer tutoring in group piano or other large classroom curricula. Investing in longer, feedback-rich pre-training can significantly strengthen outcomes for students at different stages of piano study.