Tuning the recorder
Each instrument varies 
slightly in pitch, and for 
group playing close tuning is
desired. To do this have each
person play B. Listen for the
lowest sounding B. This done
each recorder can be lowered
in pitch by twisting it apart
at the top (tuning) joint.
Shorten or lengthen each 
recorder by small amounts,
all are tuned to the lowest B.