Question

1. While I was playing the piano, I was singing a song.
2. While I was playing the piano, I sang a song.
3. While I played the piano, I sang a song.
4. While I played the piano, I was singing a song.
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Can we use all the sentences? Which ones are commonly used?

Answer 1

You've mixed verb tenses here: was playing/was singing; played/sang match.