Active control enables to assign desired time and frequency characteristics to vibrating structures. Applied to musical instruments, this technique enables them to produce new sounds radiated by their own vibrating structure, unlike sound effects applied to recordings, which are generally radiated by loudspeakers.

As part of this musical residency, composers Per Bloland and Richard Causton and STMS laboratory researcher Henri Boutin worked together to produce new piano sounds using electromagnetic transducers.

The first stage of the project involved sending signals synthesised with MaxMSP to electromagnetic actuators, placed close to the strings, in order to cause them and the piano soundboard to vibrate.

The second stage aimed to control the vibration of the complex system, consisting of a group of piano strings struck by the same hammer, coupled to each other and to the soundboard. To achieve this, a controller was placed in a feedback loop between an electromagnetic sensor and actuator, the positioning of which close to the strings was the subject of a preliminary study. The controller consists of a sum of 2nd-order bandpass filters. Their parameters are chosen on the basis of a measurement of the system's transfer function, to independently assign the desired amplitude and frequency to each of the radiated partials. This controller was first implemented on a dSPACE MicroLabBox prototyping board, offering the advantage of reducing latency to one sample period. It was then implemented with MaxMSP in a computer, introducing a higher latency but one better suited to musical performance.

This presentation will provide an opportunity to share the sounds produced during the two stages of the project in Studio 5 on IRCAM's Steinway D concert piano.