commit 731858bf0f0577de7a041f0ed8da724a81e896b2
Author: Bela Lubkin <filbo_git@armory.com>
Date:   Tue Sep 8 18:45:01 2020 -0700

    Slight refinement to tape undo: do save a short tape if there's no save
    at all yet; generally allow longer tapes to overwrite shorter, below the
    20s threshold.

diff --git a/src/tape.c b/src/tape.c
index 3be2ef1..c9a6b07 100644
--- a/src/tape.c
+++ b/src/tape.c
@@ -521,9 +521,11 @@ void SaveTapeForUndo(void)
 {
   // Only if a bit of playing has happened.  This leaves the 'precious'
   // previous run undisturbed if no real amount of playing was done.
-  // (20s could be a setting)
+  // (20s could be a setting).  Save short tape if no previous save, or
+  // to overwrite previous short save with longer one...
 
-  if (tape.length_seconds >= 20) {
+  if (tape.length_seconds >= 20 ||
+      (tapeUndo.length_seconds < 20 && tape.length_frames >= tapeUndo.length_frames)) {
     tapeUndo = tape;
   }
 }