glslViewer in this rig has no audio input — `a.fft` does not exist and reactivity must use `u_time`

The glslViewer instance in this rig is launched without an --audio flag and has no connection to the Strudel audio-analysis shim. The a.fft[...] array (which exists in the browser Hydra shim) is undefined here, and there is no audio texture via u_tex0 either. Any shader authored to react to sound renders as static or black. Motion must be driven from u_time alone (or a manual u_mouse interaction). For audio-reactive visuals the Hydra lane, with its 4-bin shim, is the correct tool.

Examples

Broken: gl_FragColor = vec4(a.fft[0]); // a.fft undefined in glslViewer Working: gl_FragColor = vec4(sin(u_time*2.0)*0.5+0.5); // time-driven

Assessment

A student pastes a Hydra audio-reactive snippet into a GLSL shader expecting it to respond to music. Explain why it renders static or black and suggest the correct alternative approach.