playing with form and genre can be risky because if you don't know what your doing with them you could completely ruin something and make it not sound good. There is a lot of songs out there that use this and will start with something very slow then the beat will completely change and most of the time it will end up sounding good but other times not
This is a good response. I agree with what you said about songs often switching beats. Sometimes it sounds good, and other times in ruins the song.
Songs that start slow then the beat gets fast is a great example of changing the genre and form.