diff --git a/doc/source_tree_layout.txt b/doc/source_tree_layout.txt
index faa5108e25..1e34dadc2e 100644
--- a/doc/source_tree_layout.txt
+++ b/doc/source_tree_layout.txt
@@ -105,8 +105,9 @@ libs/
    Control events, control lists, automation evaluation,
    parameter descriptions, incl MIDI event abstraction
 
- - libsmf (contains several non-upstreamed fixes)
-   Handling Standard MIDI File format. Abstracted to C++ in SMF.{cc,h}
+   - libsmf (contains several non-upstreamed fixes)
+     (used inside evoral)
+     Handling Standard MIDI File format. Abstracted to C++ in SMF.{cc,h}
  
  - backends
    (uses libpdb, ardouralsautil | appleutility, implements libardour interface)