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She not only plays the piano but also sings.
Literal
She [topic-は] piano [object-を] play [not only-だけでなく] song [also-も] sings.
~だけでなく ('not only X but also') is the clean, written-prose equivalent of English's correlative pair. It pairs naturally with も ('also') in the second clause to highlight the additive relationship: 'not just X — also Y.' The slightly more formal alternative ~ばかりでなく fronts ばかり instead of だけ; both are common in writing, while everyday speech tends toward simpler patterns like Xも、Y もする. 歌も歌う ('also sings songs') reuses 歌 in two different roles — first as the noun ('song'), then as the verb 歌う ('to sing') — a transparent case of the noun-verb pair that share the same kanji.