Keynotes and Characteristics by Henry Clay Allen. Originally published: 1899. Allens Keynotes is one of the most popular and widely read materia medica. The reason for its popularity being its preciseness and comprehensiveness. Dr. Allen has presented the keynote symptoms of 188 of the more commonly used remedies on a style that is very easy to read and comprehend. He has used italics and bold print to emphasise the weighting of the symptoms and has included a section on the bowel nosodes and a section on imponderables and nosodes. A classic of Homeopathic literature.