diff --git a/doc/Guidebook.mn b/doc/Guidebook.mn
index ef11975a4..ba99f46ec 100644
--- a/doc/Guidebook.mn
+++ b/doc/Guidebook.mn
@@ -3238,6 +3238,9 @@ Explored to the bottom of the Gnomish Mines and found a special item there.
 .fi
 .PL Medusa
 Defeated Medusa.
+.PL Tune
+Discovered the tune that can be used to open and close the drawbridge on
+the Castle level.
 .PL Bell
 Acquired the Bell of Opening.
 .PL Gehennom
@@ -3289,6 +3292,11 @@ corresponding achievement.
 The \fIMedusa\fP achievement is recorded if she dies for any reason,
 even if you are not directly responsible, and only if she dies.
 .pg
+The 5-note \fItune\fP can be learned via trail and error with a musical
+instrument played closely
+enough\(embut not too close!\(emto
+the Castle level's drawbridge or be given to you via prayer boon.
+.pg
 \fIBlind\fP and \fINudist\fP are also conducts, and they can only be
 enabled by setting the correspondingly named option in NETHACKOPTIONS
 or run-time configuration file prior to game start.
diff --git a/doc/Guidebook.tex b/doc/Guidebook.tex
index 3face1cba..fa994f4e6 100644
--- a/doc/Guidebook.tex
+++ b/doc/Guidebook.tex
@@ -3498,6 +3498,9 @@ Explored to the top of Sokoban and found a special item there.
 Explored to the bottom of the Gnomish Mines and found a special item there.
 \item[{\tt Medusa}]
 Defeated Medusa.
+\item[{\tt Tune}]
+Discovered the tune that can be used to open and close the drawbridge on
+the Castle level.
 \item[{\tt Bell}]
 Acquired the Bell of Opening.
 \item[{\tt Gehennom}]
@@ -3557,6 +3560,12 @@ corresponding achievement.
 The {\it Medusa\/} achievement is recorded if she dies for any reason,
 even if you are not directly responsible, and only if she dies.
 
+%.pg
+The 5-note {\it tune\/} can be learned via trail and error with a musical
+instrument played closely
+enough---but not too close!---to
+the Castle level's drawbridge or be given to you via prayer boon.
+
 %.pg
 {\it Blind\/} and {\it Nudist\/} are also conducts, and they can only be
 enabled by setting the correspondingly named option in NETHACKOPTIONS