diff --git a/src/lang.zig b/src/lang.zig
index a455a1f..03a6c52 100644
--- a/src/lang.zig
+++ b/src/lang.zig
@@ -31,6 +31,23 @@ fn LV2Command(
     };
 }
 
+fn CustomCommand(
+    comptime tag: Command.tag,
+    comptime plugin: type,
+    comptime parameters: type,
+) type {
+    return struct {
+        pub const base_tag = tag;
+        pub const command_type = CommandType.plugin_command;
+        pub const plugin_type = plugin;
+
+        base: Command,
+        split: usize,
+        index: usize,
+        parameters: LV2Parameters,
+    };
+}
+
 pub const Command = struct {
     tag: Tag,
 
@@ -113,6 +130,13 @@ pub const Command = struct {
             .saturator => Saturator,
             .vintagedelay => Vintagedelay,
 
+            .noise => Noise,
+            .wildnoise => Wildnoise,
+            .write => Write,
+            .embed => Embed,
+
+            .rotate => Rotate,
+
             else => @panic("TODO"),
         };
     }
@@ -146,8 +170,37 @@ pub const Command = struct {
 
     pub const RunQS = struct {
         pub const base_tag = Tag.runqs;
-        program: []const u8,
         base: Command,
+        program: []const u8,
+    };
+
+    pub const Noise = CustomCommand(Tag.noise, custom.RandomNoise, struct {
+        seed: f32,
+        fill_bytes: f32,
+    });
+
+    pub const Wildnoise = CustomCommand(Tag.wildnoise, custom.WildNoise, struct {
+        seed: f32,
+        fill_bytes: f32,
+    });
+
+    pub const Write = CustomCommand(Tag.write, custom.Write, struct {
+        data: f32,
+    });
+
+    pub const Embed = struct {
+        pub const base_tag = Tag.embed;
+        base: Command,
+        split: usize,
+        index: usize,
+        path: []const u8,
+    };
+
+    pub const Rotate = struct {
+        pub const base_tag = Tag.rotate;
+        base: Command,
+        deg: f32,
+        bgfill: []const u8,
     };
 
     pub const Amp = LV2Command(
@@ -362,9 +415,14 @@ pub const Command = struct {
         t4d: f32,
         t4a_db: f32,
     });
-    pub const Moddelay = LV2Command(.moddelay, "http://plugin.org.uk/swh-plugins/modDelay", struct {
-        base: f32,
-    });
+
+    pub const Moddelay = LV2Command(
+        .moddelay,
+        "http://plugin.org.uk/swh-plugins/modDelay",
+        struct {
+            base: f32,
+        },
+    );
 
     pub const Multichorus = LV2Command(.multichorus, "http://calf.sourceforge.net/plugins/MultiChorus", struct {
         min_delay: f32,
@@ -448,7 +506,7 @@ pub const Lang = struct {
         self.line = 0;
     }
     fn doError(self: *Lang, comptime fmt: []const u8, args: var) void {
-        std.debug.warn("error at line {}: ", .{self.line});
+        std.debug.warn("ERROR! at line {}: ", .{self.line});
         std.debug.warn(fmt, args);
         std.debug.warn("\n", .{});
         self.has_error = true;
@@ -471,23 +529,34 @@ pub const Lang = struct {
         // arguments...
 
         if (is_lv2_command) {
-            cmd.split = try std.fmt.parseInt(usize, tok_it.next().?, 10);
-            cmd.index = try std.fmt.parseInt(usize, tok_it.next().?, 10);
+            const split = tok_it.next();
+            if (split == null) {
+                self.doError("Expected split parameter, got EOL", .{});
+                return;
+            }
 
+            const index = tok_it.next();
+            if (index == null) {
+                self.doError("Expected index parameter, got EOL", .{});
+                return;
+            }
+
+            cmd.split = try std.fmt.parseInt(usize, split.?, 10);
+            cmd.index = try std.fmt.parseInt(usize, index.?, 10);
+
+            // All parameters for LV2 plugins are f32.
             inline for (@typeInfo(@TypeOf(cmd.parameters)).Struct.fields) |cmd_field| {
-                const arg = tok_it.next().?;
-                const argument_value = switch (cmd_field.field_type) {
-                    f32 => try std.fmt.parseFloat(f32, arg),
-                    else => @compileError("LV2 parameter struct can only have f32 fields"),
-                };
+                const maybe_arg = tok_it.next();
+                if (maybe_arg == null) {
+                    self.doError("Expected parameter for {}, got nothing", .{cmd_field.name});
+                    return;
+                }
 
-                std.debug.warn("parsing {}, arg of type {} => {}\n", .{
-                    @typeName(command_struct),
-                    @typeName(@TypeOf(argument_value)),
-                    argument_value,
-                });
+                const arg = maybe_arg.?;
+                if (cmd_field.field_type != f32)
+                    @compileError("LV2 parameter struct can only have f32 fields");
 
-                @field(cmd.parameters, cmd_field.name) = argument_value;
+                @field(cmd.parameters, cmd_field.name) = try std.fmt.parseFloat(f32, arg);
             }
         } else {
             inline for (@typeInfo(command_struct).Struct.fields) |cmd_field| {