The Cassotto is an extended space on an accordion's treble.
The Cassotto-space works as a passive filter of certain frequencies and lowers the highest range of tones (quieter) and reinforces other tones (Resonance). The sound of instruments with Cassotto therefore has a distinction from sounds of normal versions of instruments.
It is common, that not every choir in the Cassotto-space is used, but rather just the depths of choice 16' or 8'. The remains choirs are mounted on the fillings of the Diskants.
The firm Öllerer built a diatonic instrument with Cassotto, which has a small register switch two choirs with two 8' (M) choirs. In diatonic instruments the Cassotto's mounting is heavier, as a result, there is a great difference in the arrangement of pinblocks. In chromatic instruents, a Cassotto does not perform equally in every tone. The darker tones are mostly from a Stimmstock (German diatonic accordion), which are installed closer to the upper edge of the filing. As a result, the Cassotto effect is less pronounced for the Stimmstock.
Cassotto registers are only available to a few accordion models. Especially famous are the Beltuna, Pigini, Bugari and Öllerer models. In traditional German accordion making, the Cassotto barely plays a role. One can find only a few Cassotto registers in German accordions, but they can be found in the Hoher or Harmona (Klingenthal) Cassotta models, Supra & Supita II.
There is a special construction in so called the World Master Cassotta (374 + 414). "Klingenthaler Spezialcassotto" or also the "Füllungscassotto" are two known examples. These have every chord which are arranged in a normal accordion parallel. The Cassotto Effect generates a small "Canopy"("Vordach") under the Diskant Hood, that forms the Cassotto space. An advantage of this construction is to facilitate a faster response from the instrument.
The effect of a Cassotto is various instruments less pronounced with various instruments. The impact is therefore also not commonly evaluated. An individual assessment is required for each instrument. Oftentimes the Cassotto Sounds will be described as warm and chubby. Due to the filter effects, there are few strong, pronounced overtones.
There is some interaction between the types of sound materials and the Cassotto.
Frequencies between 500 Hz and 1000 Hz will be strengthened in general, but not evenly. Some frequencies will stand out more than others, over 1000 Hz everything will be rather subdued.
The sound effects of the Cassottos can be described as:
- The sound interference effect, corresponds to a spoken "o" or "a"
- The muffled sounds, in contrast, correspond to an "o" or "a" with umlauts.
- Gotthard Richter: Akustische Probleme bei Akkordeons und Mundharmonikas, Tl.1, Einführung in die allgemeinen Grundlagen. ISBN 3-925572-00-7
- Gotthard Richter: Akustische Probleme bei Akkordeons und Mundharmonikas, Tl.2, Untersuchungen spezieller Phänomene. ISBN 3-925572-01-5
- Gotthard Richter: Akkordeon. Handbuch für Musiker und Instrumentenbauer. 3. Auflage 2003, ISBN 3-7959-0569-9