diff --git a/client/src/pages/new-reel.tsx b/client/src/pages/new-reel.tsx
index 1ea3554..e1102c5 100644
--- a/client/src/pages/new-reel.tsx
+++ b/client/src/pages/new-reel.tsx
@@ -694,7 +694,7 @@ export default function NewReel() {
                                                     setSelectedTrack(null);
                                                     setCurrentStep('text');
                                                 }}>
-                                                    Passer
+                                                    Passer (garder le son de la vidéo)
                                                 </Button>
                                                 <Button onClick={() => setCurrentStep('text')}>
                                                     Continuer
@@ -1052,7 +1052,7 @@ export default function NewReel() {
                                     </div>
                                     <div className="flex justify-between">
                                         <span className="text-muted-foreground">Musique</span>
-                                        <span>{selectedTrack ? selectedTrack.title : 'Aucune'}</span>
+                                        <span>{selectedTrack ? selectedTrack.title : 'Son de la vidéo'}</span>
                                     </div>
                                     <div className="flex justify-between">
                                         <span className="text-muted-foreground">Texte</span>
diff --git a/client/src/remotion/ReelVideo.tsx b/client/src/remotion/ReelVideo.tsx
index df884d3..1472f51 100644
--- a/client/src/remotion/ReelVideo.tsx
+++ b/client/src/remotion/ReelVideo.tsx
@@ -36,9 +36,16 @@ export const ReelVideo: React.FC<ReelVideoProps> = (props) => {
 
   const videoFrames = Math.max(1, Math.floor(videoDuration * fps));
   const totalFrames = Math.max(1, Math.round(totalDuration * fps));
-  const hasAddedAudio = Boolean(mixedAudioUrl || voiceUrl || musicUrl);
+  // Le son d'origine est remplacé par la musique choisie ; sans musique, il reste
+  // en fond (baissé sous la voix). Au rendu final, il est déjà dans la piste mixée.
+  const keepVideoSound = !mixedAudioUrl && !musicUrl;
   const video = (
-    <OffthreadVideo src={videoUrl} muted={hasAddedAudio} style={{ width: "100%", height: "100%", objectFit: "cover" }} />
+    <OffthreadVideo
+      src={videoUrl}
+      muted={!keepVideoSound}
+      volume={keepVideoSound && voiceUrl ? (frame) => previewMusicVolume(frame / fps, words, 1, fadeStart) : 1}
+      style={{ width: "100%", height: "100%", objectFit: "cover" }}
+    />
   );
 
   return (
@@ -78,7 +85,7 @@ export const ReelVideo: React.FC<ReelVideoProps> = (props) => {
   );
 };
 
-/** Aperçu : la musique baisse pendant la parole et s'éteint avec le fondu final. */
+/** Aperçu : le fond sonore (musique ou son d'origine) baisse pendant la parole et s'éteint avec le fondu final. */
 function previewMusicVolume(time: number, words: TimedWord[], base: number, fadeStart: number | null): number {
   const speaking = words.some((w) => time >= w.start - 0.2 && time <= w.end + 0.3);
   const fade =
diff --git a/ffmpeg-service/app/render.py b/ffmpeg-service/app/render.py
index 89298d3..475c3df 100644
--- a/ffmpeg-service/app/render.py
+++ b/ffmpeg-service/app/render.py
@@ -102,28 +102,41 @@ def video_filters(plan: RenderPlan) -> list[str]:
     return chain
 
 
+def uses_original_audio(plan: RenderPlan) -> bool:
+    """Sans musique choisie, la bande son d'origine de la vidéo sert de fond sonore."""
+    return plan.music is None and plan.keep_original_audio
+
+
 def audio_graph(
-    plan: RenderPlan, music_idx: int | None, voice_idx: int | None
+    plan: RenderPlan, music_idx: int | None, voice_idx: int | None, original_idx: int | None = None
 ) -> tuple[list[str], str | None]:
-    """Graphe audio : voix décalée, musique bouclée et baissée sous la voix,
-    niveau final ~ -14 LUFS. Renvoie les filtres et l'étiquette de sortie."""
+    """Graphe audio : voix décalée sur un fond sonore (musique bouclée, ou à
+    défaut bande son d'origine) baissé sous la voix, niveau final ~ -14 LUFS.
+    Renvoie les filtres et l'étiquette de sortie."""
     graph: list[str] = []
     if voice_idx is not None:
         delay_ms = int(plan.voice_delay * 1000)
         graph.append(f"[{voice_idx}:a]aresample=48000,adelay={delay_ms}:all=1,apad[voice]")
-    if music_idx is not None:
-        graph.append(f"[{music_idx}:a]aresample=48000,volume={plan.music_volume:.3f}[music]")
 
-    if voice_idx is not None and music_idx is not None:
-        # La musique baisse automatiquement quand la voix parle (ducking)
+    bed = None
+    if music_idx is not None:
+        graph.append(f"[{music_idx}:a]aresample=48000,volume={plan.music_volume:.3f}[bed]")
+        bed = "bed"
+    elif original_idx is not None:
+        # Son d'origine conservé à son niveau ; il se tait après la fin de la vidéo
+        graph.append(f"[{original_idx}:a:0]aresample=48000,apad[bed]")
+        bed = "bed"
+
+    if voice_idx is not None and bed:
+        # Le fond sonore baisse automatiquement quand la voix parle (ducking)
         graph.append("[voice]asplit=2[vmix][vkey]")
-        graph.append("[music][vkey]sidechaincompress=threshold=0.02:ratio=8:attack=20:release=400[ducked]")
+        graph.append(f"[{bed}][vkey]sidechaincompress=threshold=0.02:ratio=8:attack=20:release=400[ducked]")
         graph.append("[ducked][vmix]amix=inputs=2:duration=longest:normalize=0[mix]")
         mix = "mix"
     elif voice_idx is not None:
         mix = "voice"
-    elif music_idx is not None:
-        mix = "music"
+    elif bed:
+        mix = bed
     else:
         return graph, None
 
@@ -206,14 +219,11 @@ def build_command(plan: RenderPlan) -> list[str]:
     tail.append("format=yuv420p")
     graph.append(f"[{current}]{','.join(tail)}[vout]")
 
-    audio_filters, audio_out = audio_graph(plan, music_idx, voice_idx)
+    # La vidéo (entrée 0) fournit la bande son d'origine si aucune musique n'est choisie
+    original_idx = 0 if uses_original_audio(plan) else None
+    audio_filters, audio_out = audio_graph(plan, music_idx, voice_idx, original_idx)
     graph += audio_filters
-    if audio_out:
-        audio_map = ["-map", f"[{audio_out}]"]
-    elif plan.keep_original_audio:
-        audio_map = ["-map", "0:a:0"]
-    else:
-        audio_map = []
+    audio_map = ["-map", f"[{audio_out}]"] if audio_out else []
 
     cmd += ["-filter_complex", ";".join(graph), "-map", "[vout]", *audio_map]
     cmd += ["-t", f"{total:.3f}", *_video_encoding(19, "medium")]
@@ -236,21 +246,14 @@ def build_prepared_video_command(plan: RenderPlan, output: Path) -> list[str]:
 def build_audio_mix_command(plan: RenderPlan, output: Path) -> list[str] | None:
     """Piste son finale (WAV 48 kHz stéréo), ou None s'il n'y a aucun son à produire."""
     total = f"{plan.total_duration:.3f}"
-    if not plan.music and not plan.voice:
-        if not plan.keep_original_audio:
-            return None
-        # Son d'origine seul : même niveau final que les autres Reels
-        chain = ["aresample=48000", "loudnorm=I=-14:TP=-1.5:LRA=11", "apad"]
-        if plan.ending_effect:
-            chain.append(f"afade=t=out:st={plan.fade_start:.3f}:d={FADE_SECONDS}")
-        return [
-            "ffmpeg", "-y", "-hide_banner", "-loglevel", "error", "-i", str(plan.video),
-            "-map", "0:a:0", "-af", ",".join(chain), "-t", total,
-            "-ar", "48000", "-ac", "2", "-c:a", "pcm_s16le", str(output),
-        ]  # fmt: skip
-
-    audio_args, music_idx, voice_idx, _ = _audio_inputs(plan, 0)
-    graph, audio_out = audio_graph(plan, music_idx, voice_idx)
+    audio_args, music_idx, voice_idx, index = _audio_inputs(plan, 0)
+    original_idx = None
+    if uses_original_audio(plan):
+        audio_args += ["-i", str(plan.video)]
+        original_idx = index
+    graph, audio_out = audio_graph(plan, music_idx, voice_idx, original_idx)
+    if not audio_out:
+        return None
     return [
         "ffmpeg", "-y", "-hide_banner", "-loglevel", "error", *audio_args,
         "-filter_complex", ";".join(graph), "-map", f"[{audio_out}]", "-t", total,
diff --git a/ffmpeg-service/tests/test_render.py b/ffmpeg-service/tests/test_render.py
index 56789fb..90c79ab 100644
--- a/ffmpeg-service/tests/test_render.py
+++ b/ffmpeg-service/tests/test_render.py
@@ -51,7 +51,50 @@ def test_original_audio_kept_when_nothing_added():
         video=Path("in.mp4"), video_duration=5.0, output=Path("out.mp4"), keep_original_audio=True
     )
     cmd = build_command(plan)
-    assert cmd[cmd.index("-map", cmd.index("[vout]")) + 1] == "0:a:0"
+    assert "[0:a:0]aresample=48000,apad[bed]" in _graph(cmd)
+    assert cmd[cmd.index("-map", cmd.index("[vout]")) + 1] == "[aout]"
+
+
+def test_original_audio_stays_under_the_voice_when_no_music_is_chosen():
+    plan = RenderPlan(
+        video=Path("in.mp4"),
+        video_duration=10.0,
+        output=Path("out.mp4"),
+        voice=Path("v.wav"),
+        voice_duration=4.0,
+        keep_original_audio=True,
+    )
+    graph = _graph(build_command(plan))
+    assert "[0:a:0]aresample=48000,apad[bed]" in graph
+    assert "[bed][vkey]sidechaincompress" in graph
+
+
+def test_chosen_music_replaces_the_original_audio():
+    plan = RenderPlan(
+        video=Path("in.mp4"),
+        video_duration=10.0,
+        output=Path("out.mp4"),
+        music=Path("m.mp3"),
+        keep_original_audio=True,
+    )
+    assert "0:a:0" not in _graph(build_command(plan))
+
+
+def test_prepared_audio_mix_keeps_original_audio_under_voice():
+    from app.render import build_audio_mix_command
+
+    plan = RenderPlan(
+        video=Path("in.mp4"),
+        video_duration=10.0,
+        output=Path("out.mp4"),
+        voice=Path("v.wav"),
+        voice_duration=4.0,
+        keep_original_audio=True,
+    )
+    cmd = build_audio_mix_command(plan, Path("a.wav"))
+    # Entrées : voix (0) puis vidéo d'origine (1)
+    assert cmd[cmd.index("in.mp4") - 1] == "-i"
+    assert "[1:a:0]aresample=48000,apad[bed]" in " ".join(cmd)
 
 
 def test_encoding_targets_social_networks():