The first musician to revitalize the art of glass music was Bruno Hoffman of Stuttgart, Germany. His "glass harp" was related to the ancient verrillon: sound was produced by moving wet fingers along the rims of glass bowls mounted upright on a wooden base.
The glass harp has some striking advantages when compared to the simple "musical glasses". First, the glasses are arranged in rows, making chords much easier to play: a simple major chord can be played with one hand. Second, the harp is not tuned by adding or removing water. Like the armonica bowls, the bowls of the glass harp are blown and ground until they are perfectly in tune, and, once tuned, they never need tuning again. The absence of water also improves the sound of the singing glasses, as the tuning water of the "musical glasses" attenuates sound.
Although the voice of a wine glass is familiar to everyone, the sound of the glass harp is always a surprise to the audience. People are "charmed by the sweetness of its tones", as was young Benjamin Franklin when he first heard glass music. Some compare it to a flute, a celesta, or a viola da gamba, and the sound is often described as "celestial" or as "music of the spheres" which I think means that it is not comparable to anything at all.
What music can be played on a glass harp? Well, depending on the playerís skill, quite a lot is possible. Some of the classical glass music pieces, such as Mozartís K617a, can be performed as written, but in "concertos" like the K617 Quintet or Reichardtís "Rondeau", difficulties arise from the large diameters of the lower-toned bowls (a problem that does not occur on the verrophone).
Certainly the best music for the glass harp is music written for this instrument by contemporary composers. Harald Genzmer used it in his "Variations on an Ancient Folk Song", Fred Schnaubelt wrote some fascinating solo and ensemble pieces, best exemplified by his "Concertino" for glass harp accompanied by an entire symphony orchestra.
Music written for other instruments may also be arranged for the glass harp. Best are those pieces that display the harpís ability to produce tones very quickly, so that a virtuoso performance is possible when playing only one or two parts (my favorite is an arrangement of Bachís Cello Suite No. 1).