This is a list of resources for taking the Royal Conservatory of Music’s Basic Harmony Exam.

• The Royal Conservatory, Theory Syllabus (latest edition). Tells you what you need to know.
• Robert Gauldin, Harmonic Practice in Tonal Music. Workbook available. A standard university textbook, well recommended online. I have the rather hefty workbook.
• Aldwell & Schachter, Harmony and Voice Leading. Workbook available. Another university standard, this approaches harmony from the perspective of voice leading. I’ve learned basic harmony both through the RCM syllabus (high school) and through this approach (university). Personally I much prefer the latter, as voice leading (horizontal motion) and harmony (vertical sonorities) depend on each other to exist.
• Mark Sarnecki, Harmony. I’m not familiar with this text. Only included because it follows the RCM syllabus exactly.

If you are self-studying, you can find a great deal of information online by searching. In my opinion, however, harmony is the most difficult subject to self-study by far, because what you tend to get is facts and rules whereas what you really need is an understanding of the process.

I liken harmony to math: an understanding of the logic and problem-solving process is far more useful than remembering rules and formulas. The only use my math teachers had for our textbooks was to assign homework from them. In the same way having a harmony workbook is far more useful than having a textbook, especially when if you have an instructor.