diff --git a/.gitignore b/.gitignore
index a9d940e..cad4308 100644
--- a/.gitignore
+++ b/.gitignore
@@ -28,3 +28,10 @@ __pycache__/
 # Kate leaves these beside a file it has open.
 .*.kate-swp
 Source/Emulator/rom.c
+
+# Other people's repositories, kept here to be read rather than to be built. soundThing is
+# where the synthesizer comes from and Hatchet-GPU is where the font and the scroll register
+# idea come from, and neither belongs to this one: they carry their own .git directories,
+# their own build outputs and their own compiled binaries. What this repository takes from
+# them gets vendored deliberately, with a note saying where it came from.
+/External/