An unknown Sonic Pi synth, sample, or fx name usually errors, though a bad sample name can just fall silent

Sonic Pi validates synth, sample, and fx symbol names against its built-in banks. A name that does not exist — use_synth :bass, sample :kick, with_fx :verb — usually raises an error like ‘Unknown synth :bass’ or ‘Unknown sample :kick’, though a bad sample name sometimes produces no error and simply no sound. The fix is to validate the symbol against Sonic Pi’s actual name lists and substitute a real one, such as :prophet (synth), :bd_haus (sample), or :reverb (fx). Guessing names is a frequent source of both errors and silent voices.

Examples

use_synth :bass → ‘Unknown synth :bass’; use :prophet instead. sample :kick → error or silence; use the bundled :bd_haus.

Assessment

A Sonic Pi line produces either an ‘Unknown …’ error or unexpected silence. Explain the likely cause and describe how to find a valid replacement name.