diff --git a/doc/README.md b/doc/README.md
index 34ef5d7..c342bef 100644
--- a/doc/README.md
+++ b/doc/README.md
@@ -166,6 +166,11 @@ Rotate the image by `deg` degrees, filling the resulting triangles with `bgfill`
 
 `bgfill` is a hex string, e.g `#000000`.
 
+## `embed split index path_to_file`
+
+embed an audio file in the given image. the file is opened with libsndfile,
+which means some formats, like mp3, will not be opened.
+
 ## `quicksave`
 
 Save the file on the same directory of the file specified by `load`, but