structural:summarization
Pitch pipe

The pitch pipe is a simple specialty harmonica that provides a reference pitch to singers and other instruments. The only difference between some early pitch-pipes and harmonicas is the name of the instrument, which reflected the maker's target audience. Chromatic pitch pipes, which are used by singers and choirs, give a full chromatic (12-note) octave. Pitch pipes are also sold for string players, such as violinists and guitarists; these pitch pipes usually provide the notes corresponding to the open strings.