A definition for ‘active controlled acoustic instruments’ can be found in the paper by Edgar Berdahl, Hans-Christoph Steiner, and Collin Oldham for NIME2008 called ‘Practical Hardware and Algorithms for Creating Haptic Musical Instruments [pdf]‘.
An actively controlled acoustic musical instrument is an acoustic musical instrument that is augmented with sensors, actuators, and a controller. These instruments can be considered a special case of haptic musical instruments where the interface is the entire acoustic instrument itself. For example, a monochord string can be plucked and bowed at various positions as usual, while its acoustic behavior is governed by the control hardware. Simple and appropriate control algorithms emulate passive networks of masses, springs, and dampers or implement self-sustaining oscillators.
The Haptic Drum uses haptic feedback to control the mvoement of a drum stick. It can produce high speed accurate drum rolls using just one hand so you can use your other hand to play something extra!
The Cellomobo produces feedback as a user bows a virtual string. Both of the instruments are described in more detail in the paper.