Nym Cooke, Early American Sacred Music, https://earlyamericansacredmusic.org/. (History of early church music.)

Sacred Harp Musical Heritage Association, https://fasola.org/. (Extensive descriptions and history of the Sacred Harp and Shape Note Singing. See the index, the “Introduction” pages and listings of various Sings happening in various parts of the USA. The SHMHA tab has additional resources.)

Smithsonian Institution, “Smithsonian in Your Classroom: A Shape-Note Singing Lesson,” https://www.smithsonianeducation.org/educators/lesson_plans/shapenote.pdf. (Excellent essay on the history of singing schools and shape note singing, repertoire, performance practice.)