Physical measurements and subjective characterization of pipe organ mechanical key actions

Licentiate thesis, 2013

Musical instruments do not only provide auditory or visual information but they also convey haptic feedback to the performer. One might consider that the auditory feedback is the only crucial information that the musician requires. However, as perception of most objects and events are multisensory, sensation and perception of playing a musical instrument is also multisensory. The present thesis sets out to develop a methodology to measure and characterize the properties of the organ key mechanics that determine haptic sensation of pipe organ playing. A framework is proposed here with the purpose to develop the methodology to objectively measure and subjectively characterize mechanical key action properties. The methods for the objective characterization will be explained using results of detailed measurements and a framework for subjective characterization of the haptic properties is proposed. There are a number of components in the mechanical key action that contributes to the overall force feedback to the organist. It is a complex mechanical system and no two key has identical construction. This makes it difficult to model the key action mathematically, since one needs a different form of a model for each key. Therefore, force feedback at the console as a function of key-fall and velocity was chosen to be measured to reveal the dynamic behavior of the key action. To have objective measurements and to be able to control for the key velocity, a controllable linear actuator was used to press the keys. From the results of these measurements a number of parameters were extracted to characterize dynamic system behavior. These parameters can be used for comparison of different keys within an instrument as well as overall comparison of different instruments. The study of the role of haptic sensation of organ playing requires subjective characterization of the key action. Since this part is ongoing work, only the methodology is described here. Based on an online survey among expert as well as novice organists on haptic sensation of organ playing, a set of semantic differential scales were devised. These semantic differential scales will be used in subjective experiments, with the aim to reveal the underlying dimensions of the haptic perception of the particular organs. Once the subjective characters of the key actions are revealed, they will be linked to the physical system and the objective characteristics to study the salient key action properties.