u/sokosuwimoli

I was listening to すずめ by radwimps and noticed that, while 'a' was generally pronounced as /ɑ/, its pronunciation ranged from /a/ to /ɒ/ to even /ɔ/. The very first line, I hear, /kimi no kɒ ni ɒɾɯ ɑkɔ tɔ ɑoki sem̩/. Can someone explain why the 'a' is pronounced so differently, and if this is something that only happens during singing?