。
She likes singing old songs.
Literal
She [topic-は] old songs [object-を] singing [subject-が] likes.
歌うのが好き uses the のが pattern to express 'likes doing X' — の nominalizes 歌う ('to sing') and が marks it as the subject of 好き. 昔の歌 means 'old songs' or 'songs from the past.' This is one of the most common patterns for expressing preferences: [verb]のが好き/嫌い/上手/下手.