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/machine.c

@@ -9,6 +9,7 @@
 #include "controller.h"
 #include "io.h"
 #include "video.h"
+#include "sound.h"
 #include "utility.h"
 #include "../Assembler/assembly.h"
 #include <stdio.h>
@@ -133,6 +134,7 @@ static int machineRestart(Machine *m) {
         return 0;
     }
     videoReset();
+    soundReset();
     consoleHome();
     consoleResetInput();
     initializeCPU(&m->cpu, Program, Data);
@@ -184,6 +186,10 @@ uint8_t machineStart(Machine *m, const EmulatorOptions *options, const char *pro
     // the device's, and a reset that left last program's screen up would be a reset that
     // did not happen.
     videoReset();
+    soundReset();
+    if (options->sound != NULL) {
+        soundKeepSamples();
+    }
     consoleHome();
     // The controller has to know where the memories are before anything can reach
     // them through it. Banks 0 and 1 are those two arrays.
@@ -287,6 +293,12 @@ void machineStop(Machine *m) {
     if (m->options.screen != NULL) {
         videoWriteImage(m->options.screen);
     }
+    // Every sample the machine made, for the same reason a picture is saved: there is no
+    // speaker on a machine running tests, and a sound nothing can hear is a sound nothing
+    // can check.
+    if (m->options.sound != NULL) {
+        soundWriteSamples(m->options.sound);
+    }
     if (keyboardFile != NULL) {
         consoleSetInputHook(NULL);
         fclose(keyboardFile);