diff --git a/include/clap/chmap.h b/include/clap/chmap.h
index 05717ffa..db1c5dd1 100644
--- a/include/clap/chmap.h
+++ b/include/clap/chmap.h
@@ -13,9 +13,11 @@ enum {
    // left, right
    CLAP_CHMAP_STEREO = 2,
 
-   // front left, front right, center, low, surround left, surround right
-   // surround back left, surround back right
+   // see clap_plugin_surround to inspect the exact channel layout
    CLAP_CHMAP_SURROUND = 3,
+
+   // see clap_plugin_ambisonic to inspect the exact channel layout
+   CLAP_CHMAP_AMBISONIC = 4,
 };
 typedef int32_t clap_chmap;
 
diff --git a/include/clap/ext/draft/surround.h b/include/clap/ext/draft/surround.h
new file mode 100644
index 00000000..f9fa18a6
--- /dev/null
+++ b/include/clap/ext/draft/surround.h
@@ -0,0 +1,52 @@
+#pragma once
+
+#include "../../plugin.h"
+
+static CLAP_CONSTEXPR const char CLAP_EXT_SURROUND[] = "clap.surround.draft/0";
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#pragma pack(push, CLAP_ALIGN)
+
+enum {
+   CLAP_SURROUND_FL = 0,   // Front Left
+   CLAP_SURROUND_FR = 1,   // Front Right
+   CLAP_SURROUND_FC = 2,   // Front Center
+   CLAP_SURROUND_LFE = 3,  // Low Frequency
+   CLAP_SURROUND_BL = 4,   // Back Left
+   CLAP_SURROUND_BR = 5,   // Back Right
+   CLAP_SURROUND_FLC = 6,  // Front Left of Center
+   CLAP_SURROUND_FRC = 7,  // Front Right of Center
+   CLAP_SURROUND_BC = 8,   // Back Center
+   CLAP_SURROUND_SL = 9,   // Side Left
+   CLAP_SURROUND_SR = 10,  // Side Right
+   CLAP_SURROUND_TC = 11,  // Top Center
+   CLAP_SURROUND_TFL = 12, // Front Left Height
+   CLAP_SURROUND_TFC = 13, // Front Center Height
+   CLAP_SURROUND_TFR = 14, // Front Right Height
+   CLAP_SURROUND_TBL = 15, // Rear Left Height
+   CLAP_SURROUND_TBC = 16, // Rear Center Height
+   CLAP_SURROUND_TBR = 17, // Rear Right Height
+};
+
+typedef struct clap_plugin_surround {
+   // [main-thread]
+   uint32_t (*get_channel_type)(const clap_plugin_t *plugin,
+                                bool                 is_input,
+                                uint32_t             port_index,
+                                uint32_t             channel_index);
+} clap_plugin_surround_t;
+
+typedef struct clap_host_surround {
+   // Informs the host that the channel type have changed.
+   // [main-thread]
+   void (*changed)(const clap_host_t *host);
+} clap_host_surround_t;
+
+#pragma pack(pop)
+
+#ifdef __cplusplus
+}
+#endif
\ No newline at end of file