Abstract: Choirs aim at blending the voices of different choral parts together in order to create a cohesive whole. Reaching this goal requires significant time and effort spent in rehearsals. Since joint rehearsal time is limited, amateur choir singers often practice their parts individually (e.g., at home) before the rehearsal. Over the last years, applications have become popular that offer sing-along and score following functionalities for individual rehearsals. In this work, we present a web-based interface with intonation feedback mechanism for choir rehearsal preparation. The interface combines several open-source tools that have been developed by the MIR community.