This should play if your Web browser has WebAssembly enabled (most do). Most examples will play unless they need to load files. The first time you click Play, Csound will spend a few seconds loading, then play. You can edit this code and replay it.
<CsoundSynthesizer> <CsOptions> ; Select audio/midi flags here according to platform -n ;;;no output ;-iadc ;;;uncomment -iadc if realtime audio input is needed too ; For Non-realtime ouput leave only the line below: ; -o serialWrite.wav -W ;;; for file output any platform </CsOptions> <CsInstruments> ; Required settings for WebAudio: sr = 48000 ksmps = 128 nchnls = 2 nchnls_i = 1 ; sr = 44100 ; ksmps = 500 ; the default krate can be too fast for the arduino to handle ; nchnls = 2 0dbfs = 1 instr 1 iPort serialBegin "/dev/cu.usbmodemfa131", 9600 ;connect to the arduino with baudrate = 9600 kGain init 16 ;read our knob value kVal serialRead iPort if (kVal != -1) then kGain = kVal/128 endif aSig in ;get our audio input and get its rms kRms rms aSig*kGain kRms = kRms*kRms*255 ;scale the rms to a good value for the LED and send it out serialWrite iPort, (kRms < 255 ? kRms : 255) ;must be in range: 0-255 endin </CsInstruments> <CsScore> f 1 0 1024 10 1 1 1 1 1 1 i 1 0 200 e </CsScore> </CsoundSynthesizer>