A tuning fork rings a single pure note to tune by. Dream books read it as harmony, finding your true pitch and resonating with others.
Where in your waking life have you met something like this lately?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.