Remembering lyrics from a dream is read as the unconscious putting a message into words. Forgetting them stands for something you want to say but cannot yet find.
When this appeared in your dream, what were you feeling?
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.