10 REM FILTER has no device capability -- audio synthesises and mixes but
20 REM has no filter stage; SDL3 supplies no primitive to build one from. It
30 REM is refused rather than silently ignored, so a program that asked
40 REM for a low-pass finds out it did not get one.
50 PRINT "BEFORE"
60 FILTER 1000, 1, 0, 0, 5
70 PRINT "UNREACHABLE"
