https://www.youtube.com/watch?v=yrYGqtiv8p4
I designed and constructed a battery-powered, GF1004 speaker-based instrument capable of playing a tone. I used a bipolar power source, M2 microcontroller (with necessary C# code) and mRF wireless module to produce the sinusoidal AC output with right frequency and duration requested by the wireless command. Also I introduced band-pass filter and op-amps in circuitry to filter the noises and amplify the sound.