This is the 15000th most frequent Russian word.
подсесть
To sit down next to someone.
In this sentence, 'подсел' refers to becoming emotionally or habitually attached to visiting the café.
Я случайно подсел на кафе, где подают лучшие пирожные.
I accidentally became a regular at the café where they serve the best pastries.
In this context, 'подсел' means physically sitting down close to someone.
Моя сумка закрывала место на скамейке, но он все равно подсел.
My bag was covering a spot on the bench, but he still sat down next to me.
Here, 'подсел' is used metaphorically to express developing a strong liking or addiction to the song.