PiaTune - best app for the price!
Most of the professional apps for piano tuning can do just fine on excellent pianos. The real challenges for apps are often the smaller pianos, and PiaTune outshines the rest due to both the measuring and graphing functions that allow the user to customize the tuning calculation. The developer has added specific enhancements that work well even with spinets. Combined with an effective pitch adjustment process has made getting the best sounding tunings out of so many different sized instruments during a regular tuning appointment.