That’s a technical term, that is.

For any non-musicians reading this, modulation is when a piece of music changes key.
Ah – that probably doesn’t help non-musicians… let’s put it another way.
A piece of music has a certain “feel” to it – if it’s in a major key, it generally has a kind of sunshiny, happy mood. If it then modulates – there’s that word again – to a minor key, it will generally feel as if the sun has ...