diff --git a/aegisub/src/audio_karaoke.cpp b/aegisub/src/audio_karaoke.cpp
index b62ce8f4a..24ae99243 100644
--- a/aegisub/src/audio_karaoke.cpp
+++ b/aegisub/src/audio_karaoke.cpp
@@ -754,6 +754,57 @@ int AudioKaraoke::SplitSyl (unsigned int n) {
 }
 
 
+//////////////////////////////////
+// Apply delta length to syllable
+bool AudioKaraoke::SyllableDelta(int n,int delta,int mode) {
+	wxLogDebug(_T("AudioKaraoke::SyllableDelta(n=%d, delta=%d, mode=%d)"), n, delta, mode);
+	// Get syllable and next
+	AudioKaraokeSyllable *curSyl=NULL,*nextSyl=NULL;
+	curSyl = &syllables.at(n);
+	int nkar = syllables.size();
+	if (n < nkar-1) {
+		nextSyl = &syllables.at(n+1);
+	}
+
+	// Get variables
+	int len = curSyl->duration;
+
+	// Cap delta
+	int minLen = 0;
+	if (len + delta < minLen) delta = minLen-len;
+	if (mode == 0 && nextSyl && (nextSyl->duration - delta) < minLen) delta = nextSyl->duration - minLen;
+
+	wxLogDebug(_T("AudioKaraoke::SyllableDelta: nkar=%d, len=%d, minLen=%d, delta=%d"), nkar, len, minLen, delta);
+
+	// Apply
+	if (delta != 0) {
+		wxLogDebug(_T("AudioKaraoke::SyllableDelta: delta != 0"));
+		curSyl->duration += delta;
+
+		// Normal mode
+		if (mode == 0 && nextSyl) {
+			wxLogDebug(_T("AudioKaraoke::SyllableDelta: normal mode"));
+			nextSyl->duration -= delta;
+			nextSyl->start_time += delta;
+		}
+
+		// Shift mode
+		if (mode == 1) {
+			wxLogDebug(_T("AudioKaraoke::SyllableDelta: shift mode"));
+			for (int i=n+1;i<nkar;i++) {
+				syllables.at(i).start_time += delta;
+			}
+		}
+
+		// Flag update
+		wxLogDebug(_T("AudioKaraoke::SyllableDelta: return true"));
+		return true;
+	}
+	wxLogDebug(_T("AudioKaraoke::SyllableDelta: return false"));
+	return false;
+}
+
+
 ////////////////////////////////
 // Karaoke tag menu constructor
 AudioKaraokeTagMenu::AudioKaraokeTagMenu(AudioKaraoke *_kara)
diff --git a/aegisub/src/audio_karaoke.h b/aegisub/src/audio_karaoke.h
index ec8508721..0688b6e93 100644
--- a/aegisub/src/audio_karaoke.h
+++ b/aegisub/src/audio_karaoke.h
@@ -113,6 +113,7 @@ public:
 	void Commit();
 	void SetSyllable(int n);
 	void SetSelection(int start,int end=-1);
+	bool SyllableDelta(int n,int delta,int mode);
 
 	void Join();
 	void BeginSplit();