Multiple key changes in a song?
Playing and jamming difficulties...HELP ME!
Ruth, I have to ask a question to ensure you are asking the right question.
Are you sure you are talking about "key" changes and not merely "chord" changes? The key corresponds to the keynote of the song, and in any given key, certain chords are likely. For example, a song that is in Eb will almost always have Ab and Bb as well. When a song moves from an Eb chord to a Bb chord, that is usually not a key change; it is merely a chord change. Any song will have a set of chord changes that is referred to as the chord progression, and in any given tuning, certain chord progressions are possible.
If you were to play "Go Tell Aunt Rhody," for example, in the key of Eb, there would be two chords: Eb and Bb. If you were to play "Bile Dem Cabbage Down" in the key of Eb, there would be three chords: Eb, Ab, and Bb. But in neither case is there a key change. Both songs are played in one key.
Sometimes songs really do change keys. In those cases the entire song moves from one keynote to another. And the most common key change is to move up a 4th to create an increased emotionality. For example, the Beatles song "Penny Lane" famously moves up a fourth towards the end. And sometimes that same shift can represent a lack of originality, as in the Stevie Wonder song "I Just Called to Say I Love You," where to avoid the appearance of excessive repetition the song moves up a fourth. When Whitney Houston moves up a fourth in "I Will Always Love You" it creates not only increased emotion, but increased awe because her voice demonstrates such range.
So there are songs that change keys, but they are rare. Most of the time a song begins and ends in a given key. And in that key, it will change chords several times. But if you are playing a song that moves between Eb and Bb, it is probably not changing keys, but merely changing chords.
If I am wrong here and you are indeed referring to key changes, please forgive my ramblings.