Issue 4001: Fix doc string of ly:pitch-diff

The documentation of ly:pitch-diff has got the sign wrong like forever.

diff --git a/lily/pitch-scheme.cc b/lily/pitch-scheme.cc
index 07a9a096b3051fe4dfec6ff9117ad3a9e2c2bf1c..377c4d0ff3b51cf3375805f5b646068943213750 100644 (file)
--- a/lily/pitch-scheme.cc
+++ b/lily/pitch-scheme.cc
@@ -153,8 +153,8 @@ LY_DEFINE (ly_pitch_less_p, "ly:pitch<?",
 
 LY_DEFINE (ly_pitch_diff, "ly:pitch-diff",
            2, 0, 0, (SCM pitch, SCM root),
-           "Return pitch @var{delta} such that @var{pitch} transposed by"
-           " @var{delta} equals @var{root}.")
+           "Return pitch @var{delta} such that @var{root} transposed by"
+           " @var{delta} equals @var{pitch}.")
 {
 
   LY_ASSERT_SMOB (Pitch, pitch, 1);