Why is the musical sound emitted from an open pipe more pleasant than that emitted from a closed pipe ?

Answer

A closed pipe can emit the fundamental tone and its odd harmonics. But an open pipe can emit both the odd and the even harmonics as well as the fundamental tone. So , a note emitted from an open pipe contains a larger number of constituent tones. The quality of a note depends on the number of overtones present in it. More the number of overtones present in a note, the more pleasant it sounds . This results in a higher quality of sound emitted from an open pipe .