While still in Vörde near Barmen and on tour with his Father in 1828 Friedrich built an instrument, originally intended only for use as accompanying instrument, which at first consisted of 21 different metal free reeds fastened to a wooden block in such a way that it was possible to blow the reeds individually. He fastening the reeds inside a small box "4 inches square and equally high" (in other words a cubic box with 4" sides), each of which could be made to vibrate by blowing through 21 individual "tone chambers" ("Tonlochkanzellen"). This instrument he named an "aeoline".