Expressive 2D multi-touch interfaces have in recent years moved from research prototypes to industrial products, from repurposed generic computer input devices to controllers specially designed for musical expression. A host of practicioners use this type of devices in many different ways, with different gestures and sound synthesis or transformation methods. In order to get an overview of existing and desired usages, we launched an on-line survey that collected 37 answers from practicioners in and outside of academic and design communities. In the survey we inquired about the participants' devices, their strengths and weaknesses, the layout of control dimensions, the used gestures and mappings, the synthesis software or hardware and the use of audio descriptors and machine learning. The results can inform the design of future interfaces, gesture analysis and mapping, and give directions for the need and use of machine learning for user adaptation.