From e956d19769c2cf78f95fc6f8cc15f4a34f56d495 Mon Sep 17 00:00:00 2001
From: Christoph Oelckers <coelckers@zdoom.fake>
Date: Tue, 27 Dec 2016 15:44:06 +0100
Subject: [PATCH] - preserve the factor set by I_SetMusicVolume when starting
 new music.

---
 src/sound/i_music.cpp | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/sound/i_music.cpp b/src/sound/i_music.cpp
index 630c80da5..b87ea670f 100644
--- a/src/sound/i_music.cpp
+++ b/src/sound/i_music.cpp
@@ -227,7 +227,12 @@ void MusInfo::Start(bool loop, float rel_vol, int subsong)
 {
 	if (nomusic) return;
 
-	if (rel_vol > 0.f) saved_relative_volume = relative_volume = rel_vol;
+	if (rel_vol > 0.f)
+	{
+		float factor = relative_volume / saved_relative_volume;
+		saved_relative_volume = rel_vol;
+		relative_volume = saved_relative_volume * factor;
+	}
 	Stop ();
 	Play (loop, subsong);
 	m_NotStartedYet = false;