Untitled

<html>
<head>
    <script type="text/javascript">
        var audio_context;
        var script_node;
        var sample_rate;
        var beats_per_second = 4.0;
        var samples_per_beat;

        var note_choices = [ 36, 43, 48, 51, 55, 60, 63, 67, 70, 62, 65 ];

        // middle A = 60;
        function note_to_freq(note) {
            return 440 * Math.pow(2, (note - 60) * (1.0 / 12.0));
        }

        function choose_from_array(a) {
            return a[Math.floor(Math.random() * a.length)];
        }

        window.onload = function() {
            audio_context = new AudioContext();
            sample_rate = audio_context.sampleRate;
            samples_per_beat = sample_rate / beats_per_second;

            script_node = audio_context.createScriptProcessor(4096, 0, 2);

            console.log("setting onaudioprocess");

            var notes = [ choose_from_array(note_choices), choose_from_array(note_choices) ];

            var elapsed_samples = 0;

            script_node.onaudioprocess = function(audio_processing_event) {
                // console.log(".");
                var output_buffer = audio_processing_event.outputBuffer;
                var number_of_samples = output_buffer.length;
                var number_of_channels = output_buffer.numberOfChannels;
                var output_data = [null, null];

                for (var channel = 0; channel < number_of_channels; ++channel) {
                    output_data[channel] = output_buffer.getChannelData(channel);
                }

                for (var sample = 0; sample < number_of_samples; ++sample) {
                    var envelope = 0.5 * Math.exp(-5.0 * elapsed_samples / sample_rate);
                    for (var channel = 0; channel < number_of_channels; ++channel) {
                         output_data[channel][sample] = envelope * (Math.sin(Math.PI * 2 * note_to_freq(notes[channel]) * elapsed_samples / sample_rate));
                    }

                    ++elapsed_samples;
                    if (elapsed_samples > samples_per_beat) {
                        elapsed_samples = elapsed_samples - samples_per_beat;

                        for (var channel = 0; channel < number_of_channels; ++channel) {
                            notes[channel] = choose_from_array(note_choices);
                        }
                    }
                }
            }

            console.log("making connection");
            script_node.connect(audio_context.destination);
         }

   </script>
</head>
<body>
    <audio>
No audio!
    </audio>
</body>
</html>