tunefully

From tuneful +‎ -ly.

tunefully (comparative more tunefully, superlative most tunefully)

1. In a tuneful manner.
   • 1925 July – 1926 May, A[rthur] Conan Doyle, “(please specify the chapter number)”, in The Land of Mist (eBook no. 0601351h.html), Australia: Project Gutenberg Australia, published April 2019:

     They sang very tunefully, too, for the girls had fresh voices and true ears.