(Hopefully) addressed @dan200's concerns

Push your fix to thread safety if this doesn't cut it

src/main/java/dan200/computercraft/ComputerCraft.java

@@ -294,7 +294,7 @@ public class ComputerCraft
         Config.turtlesCanPush.setComment( "If set to true, Turtles will push entities out of the way instead of stopping if there is space to do so" );
 
         Config.maxNotesPerTick = Config.config.get( Configuration.CATEGORY_GENERAL, "maxNotesPerTick", maxNotesPerTick );
-        Config.maxNotesPerTick.setComment( "Maximum amount of sounds a speaker can play at once" );
+        Config.maxNotesPerTick.setComment( "Maximum amount of notes a speaker can play at once" );
 
         for (Property property : Config.config.getCategory( Configuration.CATEGORY_GENERAL ).getOrderedValues())
         {
@@ -335,7 +335,7 @@ public class ComputerCraft
         turtlesObeyBlockProtection = Config.turtlesObeyBlockProtection.getBoolean();
         turtlesCanPush = Config.turtlesCanPush.getBoolean();
 
-        maximumFilesOpen = Math.max(1, Config.maximumFilesOpen.getInt());
+        maxNotesPerTick = Math.max(1, Config.maxNotesPerTick.getInt());
 
         Config.config.save();
     }

src/main/java/dan200/computercraft/shared/peripheral/speaker/SoundTask.java

@@ -1,45 +0,0 @@
-/*
- * This file is part of ComputerCraft - http://www.computercraft.info
- * Copyright Daniel Ratcliffe, 2011-2016. Do not distribute without permission.
- * Send enquiries to dratcliffe@gmail.com
- */
-
-package dan200.computercraft.shared.peripheral.speaker;
-
-import dan200.computercraft.api.lua.ILuaTask;
-import dan200.computercraft.api.lua.LuaException;
-import net.minecraft.util.ResourceLocation;
-import net.minecraft.util.SoundCategory;
-import net.minecraft.util.SoundEvent;
-import net.minecraft.util.math.BlockPos;
-import net.minecraft.world.World;
-
-import javax.annotation.Nullable;
-
-public class SoundTask implements ILuaTask
-{
-
-    SoundTask(World world, BlockPos pos, ResourceLocation resourceName, float volume, float pitch)
-    {
-        m_world = world;
-        m_pos = pos;
-        m_resourceName = resourceName;
-        m_volume = volume;
-        m_pitch = pitch;
-    }
-
-    // Fields
-    private World m_world;
-    private BlockPos m_pos;
-    private ResourceLocation m_resourceName;
-    private float m_volume;
-    private float m_pitch;
-
-
-    @Nullable
-    @Override
-    public Object[] execute() throws LuaException {
-        m_world.playSound(null, m_pos, new SoundEvent(m_resourceName), SoundCategory.RECORDS, m_volume, m_pitch);
-        return new Object[]{};
-    }
-}

src/main/java/dan200/computercraft/shared/peripheral/speaker/SpeakerPeripheral.java

@@ -8,15 +8,17 @@ package dan200.computercraft.shared.peripheral.speaker;
 
 import dan200.computercraft.ComputerCraft;
 import dan200.computercraft.api.lua.ILuaContext;
+import dan200.computercraft.api.lua.ILuaTask;
 import dan200.computercraft.api.lua.LuaException;
 import dan200.computercraft.api.peripheral.IComputerAccess;
 import dan200.computercraft.api.peripheral.IPeripheral;
 import net.minecraft.util.ResourceLocation;
+import net.minecraft.util.SoundCategory;
 import net.minecraft.util.SoundEvent;
 import net.minecraft.util.math.BlockPos;
 import net.minecraft.world.World;
-
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 
 public class SpeakerPeripheral implements IPeripheral {
 
@@ -38,7 +40,7 @@ public class SpeakerPeripheral implements IPeripheral {
         m_speaker = speaker;
     }
 
-    public void update() {
+    public synchronized void update() {
         m_clock++;
         m_notesThisTick = 0;
     }
@@ -124,7 +126,8 @@ public class SpeakerPeripheral implements IPeripheral {
         }
     }
 
-    private Object[] playNote(Object[] arguments, ILuaContext context) throws LuaException
+    @Nonnull
+    private synchronized Object[] playNote(Object[] arguments, ILuaContext context) throws LuaException
     {
         double volume = 1f;
         double pitch = 1f;
@@ -147,29 +150,24 @@ public class SpeakerPeripheral implements IPeripheral {
 
         if (arguments.length > 1)
         {
-            if (!(arguments[1] instanceof Double))   // Arg wrong type
+            if (!(arguments[1] instanceof Double) && !(arguments[1] == null))   // Arg wrong type
             {
                 throw new LuaException("Expected string, number (optional), number (optional)");
             }
-            volume = ((Double) arguments[1]).floatValue();
+            volume = arguments[1] != null ? ((Double) arguments[1]).floatValue() : 1f;
 
         }
 
         if (arguments.length > 2)
         {
-            if (!(arguments[1] instanceof Double))  // Arg wrong type
+            if (!(arguments[1] instanceof Double) && !(arguments[2] == null))  // Arg wrong type
             {
                 throw new LuaException("Expected string, number (optional), number (optional)");
             }
-            pitch = ((Double) arguments[2]).floatValue();
+            pitch = arguments[2] != null ? ((Double) arguments[2]).floatValue() : 1f;
         }
 
-        if (arguments.length > 3)
+        // If the resource location for note block notes changes, this method call will need to be updated
-        {
-            throw new LuaException("Expected string, number (optional), number (optional)");
-        }
-
-        // If the resource location for noteblock notes changes, this method call will need to be updated
         Object[] returnValue = playSound(new Object[] {"block.note." + arguments[0], volume, Math.pow(2d, (pitch - 12) / 12d)}, context, true);
 
         if (returnValue[0] instanceof Boolean && (Boolean) returnValue[0])
@@ -181,7 +179,8 @@ public class SpeakerPeripheral implements IPeripheral {
 
     }
 
-    private Object[] playSound(Object[] arguments, ILuaContext context, boolean isNote) throws LuaException
+    @Nonnull
+    private synchronized Object[] playSound(Object[] arguments, ILuaContext context, boolean isNote) throws LuaException
     {
 
         float volume = 1f;
@@ -196,31 +195,29 @@ public class SpeakerPeripheral implements IPeripheral {
         if (!(arguments[0] instanceof String)) // Arg wrong type
         {
             throw new LuaException("Expected string, number (optional), number (optional)");
+
         }
 
         if (arguments.length > 1)
         {
-            if (!(arguments[1] instanceof Double))  // Arg wrong type
+            if (!(arguments[1] instanceof Double) && !(arguments[1] == null))  // Arg wrong type
             {
                 throw new LuaException("Expected string, number (optional), number (optional)");
             }
-            volume = ((Double) arguments[1]).floatValue();
+
+            volume = arguments[1] != null ? ((Double) arguments[1]).floatValue() : 1f;
 
         }
 
         if (arguments.length > 2)
         {
-            if (!(arguments[2] instanceof Double))  // Arg wrong type
+            if (!(arguments[2] instanceof Double) && !(arguments[2] == null))  // Arg wrong type
             {
                 throw new LuaException("Expected string, number (optional), number (optional)");
             }
-            pitch = ((Double) arguments[2]).floatValue();
+            pitch = arguments[2] != null ? ((Double) arguments[2]).floatValue() : 1f;
         }
 
-        if (arguments.length > 3)
-        {
-            throw new LuaException("Expected string, number (optional), number (optional)");
-        }
 
         ResourceLocation resourceName = new ResourceLocation((String) arguments[0]);
 
@@ -229,7 +226,24 @@ public class SpeakerPeripheral implements IPeripheral {
 
             if (SoundEvent.REGISTRY.containsKey(resourceName))
             {
-                context.issueMainThreadTask(new SoundTask(getWorld(), getPos(), resourceName, volume, pitch));
+
+                final World world = getWorld();
+                final BlockPos pos = getPos();
+                final ResourceLocation resource = resourceName;
+                final float vol = volume;
+                final float soundPitch = pitch;
+
+                context.issueMainThreadTask(new ILuaTask() {
+
+                    @Nullable
+                    @Override
+                    public Object[] execute() throws LuaException {
+                        world.playSound(null, pos, new SoundEvent(resource), SoundCategory.RECORDS, vol, soundPitch);
+                        return null;
+                    }
+
+                });
+
                 m_lastPlayTime = m_clock;
                 return new Object[]{true}; // Success, return true
             }

src/main/java/dan200/computercraft/shared/peripheral/speaker/TileSpeaker.java

@@ -6,9 +6,9 @@
 
 package dan200.computercraft.shared.peripheral.speaker;
 
-        import dan200.computercraft.api.peripheral.IPeripheral;
+import dan200.computercraft.api.peripheral.IPeripheral;
-        import dan200.computercraft.shared.peripheral.common.TilePeripheralBase;
+import dan200.computercraft.shared.peripheral.common.TilePeripheralBase;
-        import net.minecraft.util.EnumFacing;
+import net.minecraft.util.EnumFacing;
 
 public class TileSpeaker extends TilePeripheralBase
 {

src/main/java/dan200/computercraft/shared/proxy/ComputerCraftProxyCommon.java

@@ -555,15 +555,15 @@ public abstract class ComputerCraftProxyCommon implements IComputerCraftProxy
     private void registerTileEntities()
     {
         // Tile Entities
-        GameRegistry.registerTileEntity( TileComputer.class, "computer" );
+        registerTileEntity( TileComputer.class, "computer" );
-        GameRegistry.registerTileEntity( TileDiskDrive.class, "diskdrive" );
+        registerTileEntity( TileDiskDrive.class, "diskdrive" );
-        GameRegistry.registerTileEntity( TileWirelessModem.class, "wirelessmodem" );
+        registerTileEntity( TileWirelessModem.class, "wirelessmodem" );
-        GameRegistry.registerTileEntity( TileMonitor.class, "monitor" );
+        registerTileEntity( TileMonitor.class, "monitor" );
-        GameRegistry.registerTileEntity( TilePrinter.class, "ccprinter" );
+        registerTileEntity( TilePrinter.class, "ccprinter" );
-        GameRegistry.registerTileEntity( TileCable.class, "wiredmodem" );
+        registerTileEntity( TileCable.class, "wiredmodem" );
-        GameRegistry.registerTileEntity( TileCommandComputer.class, "command_computer" );
+        registerTileEntity( TileCommandComputer.class, "command_computer" );
-        GameRegistry.registerTileEntity( TileAdvancedModem.class, "advanced_modem" );
+        registerTileEntity( TileAdvancedModem.class, "advanced_modem" );
-        GameRegistry.registerTileEntity( TileSpeaker.class, "speaker" );
+        registerTileEntity( TileSpeaker.class, "speaker" );
 
         // Register peripheral providers
         ComputerCraftAPI.registerPeripheralProvider( new DefaultPeripheralProvider() );

src/main/resources/assets/computercraft/lang/en_US.lang

@@ -59,3 +59,4 @@ gui.computercraft:config.advanced_turtle_fuel_limit=Advanced Turtle fuel limit
 gui.computercraft:config.turtles_obey_block_protection=Turtles obey block protection
 gui.computercraft:config.turtles_can_push=Turtles can push entities
 gui.computercraft:config.maximum_files_open=Maximum files open per computer
+gui.computercraft:config.max_notes_per_tick=Maximum notes that a computer can play at once