Give the machine a sound device

Four channels on ports 0x40 to 0x4F, each one a whole soundThing voice:
two oscillators, two envelopes, a filter and the routing between them. A
channel keeps its patch between notes, so a program sets an instrument up
once and then plays it.

Six ports rather than forty, because a voice has around forty settings and
four of them would spend more than half the port space on one device.
There is a selector and a value instead: say which channel, say which
setting, write it. That is three writes to change a setting and two to
play a note, which is the right way round - patches are loaded, notes are
played in an inner loop.

Samples come from the machine's clock and not the host's: 48,000 a second
of emulated time, worked out in whole numbers so it never drifts. A
million cycles is exactly 48,000 samples on any host at any speed, which
is what makes a sound something a test can compare. --sound writes them
out, the way --screen writes a picture, for the same reason: the suite has
no speaker.

Tests/sound.sh is 22 checks and found three real defects the first time it
ran, all the same shape - a synthesizer written for a patch editor, wired
up as hardware and inheriting the editor's assumptions:

  - Only one voice had an oscillator switched on, so three of the four
    channels could not make a sound whatever was written to them.
  - That voice's oscillator arrived at full gain and every other one
    arrived at nothing, an asymmetry with no reason behind it.
  - A note with no sustain is silent but not over, so the obvious way to
    wait for a sound to finish waits for ever.

The first two are fixed by the device defining its own power-on state
rather than inheriting synthInit's: every channel arrives able to make a
sound, so writing a note number is the whole of playing a note. The third
was already written into the manual as advice, an hour before the check
existed. The check disagreed with the documentation and the check was
right; the manual now says the one rule, which is that a note sounds until
the gate is dropped.

Programs/Examples/tune.asm plays eight notes, taking its tempo from the
screen's frame interrupt because that is the only regular beat this
machine has. It spends 99.8% of its cycles asleep in WAIT.

Voyager has no speaker yet - this is the device and its tests. Playing the
samples out of the window is the next commit.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW

Source/Emulator/utility.c

@@ -34,6 +34,9 @@ void printHelp(const char *programName) {
     printf("                    keyboard rather than a terminal. Which means the console does\n");
     printf("                    its own line editing, the way it must when a window is open\n");
     printf("                    and there is no terminal behind it to do it.\n");
+    printf("  -N, --sound FILE  Save every sample the machine made, as raw signed 16 bit\n");
+    printf("                    at 48kHz. What --screen is for a picture: the only way to\n");
+    printf("                    check a sound on a machine with no speaker.\n");
     printf("  -h, --help        Display this help message.\n");
 }
 
@@ -47,6 +50,7 @@ uint8_t parseOptions(int argc, char *argv[], EmulatorOptions *options) {
         {"disk-cycles", required_argument, 0, 'L'},
         {"screen", required_argument, 0, 'S'},
         {"keyboard", required_argument, 0, 'K'},
+        {"sound", required_argument, 0, 'N'},
         {"help",   no_argument,       0, 'h'},
         {0,        0,                 0,  0 }
         };
@@ -61,9 +65,10 @@ uint8_t parseOptions(int argc, char *argv[], EmulatorOptions *options) {
     options->diskCycles = 0;
     options->screen = NULL;
     options->keyboard = NULL;
+    options->sound = NULL;
 
     // Parse options
-    while ((opt = getopt_long(argc, argv, "dc:fhD:WL:S:K:", long_options, &option_index)) != -1) {
+    while ((opt = getopt_long(argc, argv, "dc:fhD:WL:S:K:N:", long_options, &option_index)) != -1) {
         switch (opt) {
             case 'd':
                 options->debug = 1;
@@ -99,6 +104,9 @@ uint8_t parseOptions(int argc, char *argv[], EmulatorOptions *options) {
             case 'K':
                 options->keyboard = optarg;
             break;
+            case 'N':
+                options->sound = optarg;
+            break;
             case 'h':
                 printHelp(argv[0]);
                 return OPTIONS_HELP;