HevyMetl heart => Gain g => dac;
    while(true) {
        1 => g.gain;
        std.mtof(24) => heart.freq;
        heart.noteOn(0.5);
        0.1::second => now;
        0 => g.gain;
        0.1::second => now;
        1 => g.gain;
        0.1::second => now;
        0 => g.gain;
        2::second => now;
    }