Your love is surprising, I can feel it rising
All the joy that's growing deep inside of me
What is the 'it' in the clause, 'I can feel it rising'?
(a) God's love? or
(b) the 'joy that's growing deep inside of me'? or
(c) is the joy inside me God's love and so 'it' refers to both of them?
The most natural reading of the song is (a) although, as we shall see, (a) might easily be taken to imply (c). (b) is not impossible though somewhat unnatural.
Does it matter? Well, it does a bit. Here's why. I think that (a) is very unclear. What would it mean for God's love to rise within me? The most natural meaning is to take it with the following line and identify the rising love of God with the growing joy (i.e., to embrace view (c)). and (c) come very close to unintentional idolatry. Someone certainly would be on highly questionable ground if they thought about what they were singing and affirmed (c).
God cannot be identified (in a strong sense) with any part of his creation. God's love might inspire deep joy to rise within me but it is not identical with that joy. God's love is not a fuzzy feeling that I have. To speak of God's love is to speak about God not about my emotions.
Now religious language is not always super-precise and one could construe view (c) as a loose way of saying, 'Your love surprises me and causes joy to rise deep within me'. Indeed, I am pretty sure that Brenton Brown intended to say that I am am pretty sure that most who sing the song would translate it that way without even thinking about it. So there is not much harm done.
But it would be great if songwriters - who do have plenty of time to craft their songs before releasing them to the public - thought even more carefully about theology and potential misreadings of their lyrics.