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 ; Audio out Audio in -odac -Ma -Q1 ;;;realtime audio out and midi out and midi in (all midi inputs) </CsOptions> <CsInstruments> ; Required settings for WebAudio: sr = 48000 ksmps = 128 nchnls = 2 nchnls_i = 1 ; sr = 44100 ; ksmps = 32 ; nchnls = 2 0dbfs = 1 instr 1 midiout_i 192, 1, 21, 0 ;program change to instr. 21 inum notnum ivel veloc midion 1, inum, ivel endin </CsInstruments> <CsScore> i 1 0 3 80 100 ;play note for 3 seconds e </CsScore> </CsoundSynthesizer>