The riff is

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Em
By the margin of the ocean,
Em
One pleasant evening in the month of June,
Em
When all those feathered songsters
Em
Their pleasant notes did sweetly tune,
      G               Am
'Twas there I spied a female
      C                        Em
Who seemed to be in grief or woe,
      G               Am
Conversing with young Bonaparte
      C                         Em
Concerning the Bonnie Bunch of Roses-O.