Ambigous harmony

In many song the homekey is chrystal clear from start to end of the song. Often the song opens and closes with the tonic chord, for example in "Dear Friends". They say the song has strong tonality. In many songs or song passages the tonality is weak, and you can hardly determine what is the homekey. For example the intro of "Death On Two Legs", "'39", or the chorus of "Princes Of The Universe". Sometimes you can interpret the harmony being in two or three different keys. For example the intro of "Coming Soon". The analyses sometimes include more altarnatives, sometimes none since in an ambigous harmony the chord functions are ambigous too.