In this paper, we discuss the use of the clothesline as ametaphor for designing a musical interface called Airer Choir. This interactive installation is based on the function ofan ordinary object that is not a traditional instrument, andhanging articles of clothing is literally the gesture to use theinterface. Based on this metaphor, a musical interface withhigh transparency was designed. Using the metaphor, weexplored the possibilities for recognizing of input gesturesand creating sonic events by mapping data to sound. Thus,four different types of Airer Choir were developed. By classifying the interfaces, we concluded that various musicalexpressions are possible by using the same metaphor.