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> -+rtaudio=JACK -b 64 --sched -o dac:system:playback_ </CsOptions> <CsInstruments> ; sr = 44100 ; ksmps = 16 nchnls = 2 instr 1 jacktransport p4, p5 endin instr 2 jacktransport p4 endin </CsInstruments> <CsScore> i2 0 5 1; play i2 5 1 0; stop i1 6 5 1 2 ; move at 2 seconds and start playing back i1 11 1 0 0 ; stop and rewind e </CsScore> </CsoundSynthesizer>