I'm studying harmony and start to make roman numeral analysis on Bach pieces. I often mistake a II (second degree) for a secondary dominant on the 2nd degree(V7 of V). I guess there are some notes ...
It has to be prety basic but I never understood how it is conventionally explained. Usually a pop song has a fixed key like in: Cmajor: Verse: C-Am-F-G Bridge: Am-G, Am-G Chorus: F-G-Am How is ...