K&K pickup and mic systems can be used on a host of other instruments. Some of the more popular ones are listed here.
Tenor guitars are growing in popularity. The usual option is the 2-head Twin Spot bridgeplate transducer, although other hybrid pickup/mic systems can be supplied if preferred.
For cittern or bouzouki type instruments I usually recommend the Twin Spot for smaller-bodied instruments and the Pure Archtop for larger/deeper/archtop instruments. If you prefer an externally mounted system for a floating bridge type folk instrument then the Definity or Definity Pro is the way to go.
Piano and accordion systems are also listed here. The piano system was developed in cooperation with the renowned German piano manufacturer Seiler Pianos. The accordion system provides one of the best ways of ensuring a good balance between treble and bass.
Also see multi-use systems listings.