What is the key of the flute for the song "Busy carrying grain"?

The original key of this song is D, with A flute barrel tone as 2, there are also G flute, with barrel tone as 2, some people use F key, but it is a little too low, for this song, the expressive power is a little too weak.

"Busy Transporting Grain by Whipping Horses":

This piece was the most popular in the 1960s, and it is a typical solo piece in the A, B, A three-part structure of flute music. The melody of the piece is evolved from the Northeast's rice-planting song and dance, and the cheerful, bright, fast upper and lower calendar tones of the piece portray the scene of raising the whip and urging the horse in a very graphic way, and the tone pattern of the melody makes the image of the carriage on the move even more musical, which made the piece a very successful flute piece at that time.