This tiny transmitter has lower quality of sounds and unstable frequency. Every cable of audio input and battery influences the output frequecyhy--- this can be a bit solved by using thin coaxial cables for these sections. But the advantage is that you need not special materials such as a variable capacitance diode. In stead of that, this can cover at least 10 meter radius. This should be good for your artistic installation.

The schimatic is supposed to use copper coated plate that is familiar with my design. When it is difficult to obtain, you can use even "porous circuit board" that is popular in electronic hobby. The schematic is here. I suggest you use the reverse by directly solder the parts to it becasue this convenient for possible cut-and-paste and for the electro-magnetic performance.

obtained from Tetsuo Kogawa's website: