diff --git a/Examples/CompleteHir3.bmb b/Examples/CompleteHir3.bmb
new file mode 100644
index 0000000..7acd904
--- /dev/null
+++ b/Examples/CompleteHir3.bmb
@@ -0,0 +1,23 @@
+{Sets some context information.}
+set_scale 2 1 4 1 4
+set_root 60
+set_tempo 128
+set_sounds 108 107
+
+{Defines 3 2-multi-patterns.}
+multi_pattern mpat_1 1 1 0 0 2 2 1 1 ; -5 * * * 0 * * *
+multi_pattern mpat_2 -1 * 0 * 1 * ; * 0 * * 0 *
+multi_pattern mpat_3 0 * ; * 0
+
+{Defines 4 colored 2-multi-patterns from the previous 2-multi-patterns.}
+colorize cpat_1 mpat_1 c1 c2 c1
+colorize cpat_2 mpat_1 c1 c1 c2
+colorize cpat_3 mpat_2 c1 c1 c2
+colorize cpat_4 mpat_3 c1 c1
+
+{Creates a new 2-multi-pattern mpat_4 obtained by using the partial random generation
+ algorithm with k := 32, c1 as initial color, and cpat_1, cpat_2, cpat_3, and cpat_4 as
+ rules.}
+generate mpat_4 partial 32 c1 cpat_1 cpat_2 cpat_3 cpat_4
+play mpat_4
+
diff --git a/Examples/Sounds.bmb b/Examples/Sounds.bmb
index 112b749..b741cb7 100644
--- a/Examples/Sounds.bmb
+++ b/Examples/Sounds.bmb
@@ -1,4 +1,4 @@
-{ By default, the MIDI sound of all voices is the "Acoustic Grand Piano" of code 0.}
+{By default, the MIDI sound of all voices is the "Acoustic Grand Piano" of code 0.}
 multi_pattern p1 1 -1 0 * * 7 ; 3 * 2 * 0 0
 play p1
 
diff --git a/Sources/Program.ml b/Sources/Program.ml
index 5fe9e4c..a63966a 100644
--- a/Sources/Program.ml
+++ b/Sources/Program.ml
@@ -255,6 +255,8 @@ let execute_instruction instr st =
         |MultiPattern (name, mpat) -> begin
             if not (is_name name) then
                 raise (ExecutionError "Bad multi-pattern name.");
+            if not (MultiPattern.is_multi_pattern mpat) then
+                raise (ExecutionError "Bad multi-pattern.");
             let st' = add_multi_pattern st name mpat in
             Printf.printf "%s Multi-pattern added." output_mark;
             print_newline ();