It's the feeling behind the words which effects it. As 'I love you' is variable as most people say, 'I love you' carelessly to anyone or anything they show emotional affection to. When I'm sure they love their loved one more, we've deteriorated the word, love.
So of course it's going to have a positive effect being positive and having positive music around. As all good music is, is frequencies in harmony, we enjoy harmony. Just as music effects our mood so does it effect the plants 'mood'.