A ChucK UGen only produces audio if it is chucked transitively to `dac`

In ChucK, audio only reaches the speakers through the special dac UGen. Any UGen not connected — directly or via a chain — to dac is silent, or routed to blackhole (which ticks for control/analysis purposes but produces no audio). A common mistake is creating an oscillator and connecting it to an intermediate Gain object without completing the chain to dac; the whole voice is then silent even though it is ‘running’.

Examples

SinOsc s => dac; // audible SinOsc s => Gain g; // silent — g not chucked to dac SinOsc s => Gain g => dac; // audible again

Assessment

Trace a ChucK signal chain and identify which voices are audible: (a) SinOsc => blackhole, (b) SinOsc => Gain, (c) SinOsc => Gain => dac. Explain the role of blackhole.