Glass harmonica from Schönborn Castle in Geisenheim.

The glass harmonica has been in the possession of the Frankfurt Historical Museum since 1905. It is an outstanding instrument of the historical music collection. An inventory revision was taken as an opportunity to carry out necessary conservation work. In the relevant literature, the glass harmonica is described as a development of Benjamin Franklin: The so-called rubbing idiophone developed into a sought-after musical instrument at the end of the 18th century. Up to the beginning of the 19th century, the glass organ was very popular; famous composers such as Wolfgang Amadeus Mozart or Johann Christian Müller composed pieces of music for the glass harmonica. At the beginning of the 20th century Richard Strauss again integrated the glass harmonica in his opera compositions.

The glass harmonica in the Frankfurt Historical Museum measures 0.91 m in height, 1.225 m in width and 0.45 m in depth. Conversation work included strenghtening loose veneer areas with glutin glue and cleaning the original lacquer surface with distilled water. Missing areas such as moldings on the square tapered feet could be supplemented with walnut and then tuned with watercolor. The gloss level of the imperfections was adjusted to the original environment with Dammer varnish.

The interlocking glass bells rest on a common horizontal metal axle. The glass bells are set in motion by operating a foot pedal. The sound is produced by touching the edges of the bells with a wet finger. The sounding body is a wooden body constructed of walnut and veneered softwood with walnut. To math the spirit and taste of the time, the walnut is dyed a deep red and finished with a slightly glossy reddish-brown lacquer surface. The metal applications that conceal the screw function of the legs on the side surfaces are gilded. The legs could be disassembled, which is a travel transport convenience. The foot pedal is attached to the legs by a plug-in mechanism. A leather strap provides power transmission to the axle with the glass bells.

In the course of the preoccupation with historical performance practice, historical musical instruments have once again become the focus of public interest in recent years. Since they were subject to the respective fashions of the time and technical requirements, they underwent permanent changes or were completely replaced by new models. Particularly in the Renaissance and early Baroque periods, there existed a large number of instrument types that are no longer known today or whose modern successors (e.g. oboe, bassoon) bear only a superficial resemblance to the original instruments (pommer, dulcian).
In addition to an alto pommer made by the famous Denner family of instrument makers in Nuremberg at the beginning of the 18th century, the historical museum also owns a no less valuable dulcian, which, with its incised date of 1605 and the Frankfurt eagle, refers to the so-called Kapellmusik (chapel music) in Frankfurt's Barfüßerkirche, which was founded towards the end of the 16th century. The task of the instrumentalists, whose number varied between eight and eleven, was initially to provide musical accompaniment to church services in the Barfüßerkirche. Later they also played at secular occasions. Their instruments were not, as is common today, the property of the musicians, but were made available to them. Since wind instruments could not be returned at will, it was necessary to have instruments tuned to pitch. In the absence of standardized orchestras, each ensemble thus had its own sound with an individual tuning tone.

Among the total of twelve top-class instruments of chapel music in the historical museum, one instrument can be directly associated with the name of an instrument maker. This is the column recorder by the instrument maker Hans Rauch Schratt(enbach)s. Only five other column recorders of this instrument maker family are known to date. They can be combined to an instrument set of different pitches.

Two instrument sets of the Frankfurt Kapellmusik with their corresponding cases show how such a set looked like. Although not all of the instruments have survived, the pitches of the instruments missing today can be reconstructed from the length of the chuck tubes.

The earliest woodwind instruments in the collection, probably from an Italian workshop, are part of one of the two instrument sets. A record in the "inventarium Librorum Instrumentorum Musicorum" of the Kapellmeister of the Barfüßerkirche, J.A. Herbst, dates these flutes to before 1626. An X-ray examination carried out in October 2009 in the Frankfurt Archaeological Museum was able to provide interesting insights into the inner workings of the unusually full-round, strongly conical tenor recorders, so that statements can now be made about the exact technique of the one-piece instruments. Further secrets are to be revealed in the future and will provide us with information about the sound of these instruments, which are extremely rare today.