diff --git a/sw_usb_audio/app_usb_aud_fosi_c1/src/extensions/extra_i2s.xc b/sw_usb_audio/app_usb_aud_fosi_c1/src/extensions/extra_i2s.xc
index 2cf7f48..b019a3d 100644
--- a/sw_usb_audio/app_usb_aud_fosi_c1/src/extensions/extra_i2s.xc
+++ b/sw_usb_audio/app_usb_aud_fosi_c1/src/extensions/extra_i2s.xc
@@ -76,9 +76,9 @@ void UserBufferManagement(unsigned sampsFromUsbToAudio[], unsigned sampsFromAudi
         }
 
 #if C1_DFS_EN
-        /* Proactive output mute around FPS on/off: zeroes the playback path for
-         * ~C1_SWITCH_MUTE_SAMPLES after each toggle, masking the path-switch pop
-         * and the stale FPS data tail until the flushed pipeline refills. */
+        /* Smooth fade-out / hold / fade-in around the FPS on/off toggle: masks
+         * the path-switch pop and the stale FPS data tail without the click a
+         * hard zero would make at the mute edges. gain is 0..1024 (Q10), 1024 = unity. */
         {
             static unsigned sw_mute_samps = 0;
             static unsigned prev_sw_mute = 0;
@@ -86,9 +86,20 @@ void UserBufferManagement(unsigned sampsFromUsbToAudio[], unsigned sampsFromAudi
             GET_SHARED_GLOBAL(sw_mute, g_fps_switch_mute);
             if (sw_mute)
             {
-                if (!prev_sw_mute) sw_mute_samps = 0;   /* re-armed: restart count */
-                sampsFromUsbToAudio[0] = 0;
-                sampsFromUsbToAudio[1] = 0;
+                unsigned n, gain;
+                int s0, s1;
+                if (!prev_sw_mute) sw_mute_samps = 0;   /* re-armed: restart at fade-out */
+                n = sw_mute_samps;
+                if (n < C1_SWITCH_FADE_SAMPLES)
+                    gain = 1024u - (n * 1024u / C1_SWITCH_FADE_SAMPLES);                                  /* fade out: 1024 -> 0 */
+                else if (n >= C1_SWITCH_MUTE_SAMPLES - C1_SWITCH_FADE_SAMPLES)
+                    gain = ((n - (C1_SWITCH_MUTE_SAMPLES - C1_SWITCH_FADE_SAMPLES)) * 1024u / C1_SWITCH_FADE_SAMPLES); /* fade in: 0 -> ~1024 */
+                else
+                    gain = 0;                                                                              /* hold */
+                s0 = (int)sampsFromUsbToAudio[0];
+                s1 = (int)sampsFromUsbToAudio[1];
+                sampsFromUsbToAudio[0] = (unsigned)(((long long)s0 * gain) >> 10);
+                sampsFromUsbToAudio[1] = (unsigned)(((long long)s1 * gain) >> 10);
                 if (++sw_mute_samps >= C1_SWITCH_MUTE_SAMPLES)
                 {
                     SET_SHARED_GLOBAL(g_fps_switch_mute, 0);
diff --git a/sw_usb_audio/app_usb_aud_fosi_c1/src/extensions/tile1_clk.h b/sw_usb_audio/app_usb_aud_fosi_c1/src/extensions/tile1_clk.h
index 781810c..76f021f 100644
--- a/sw_usb_audio/app_usb_aud_fosi_c1/src/extensions/tile1_clk.h
+++ b/sw_usb_audio/app_usb_aud_fosi_c1/src/extensions/tile1_clk.h
@@ -62,6 +62,12 @@
  * pipeline flush + 1-frame refill. 2880 ~= 60 ms. */
 #define C1_SWITCH_MUTE_SAMPLES     2880
 
+/* Per-edge fade length (fade-out and fade-in each) inside the mute window, in
+ * audio samples (@ 48 kHz). The window fades out over this many samples, holds
+ * near-zero, then fades in -- avoids the click a hard mute makes at its edges.
+ * Must be <= C1_SWITCH_MUTE_SAMPLES/2. 512 ~= 10.7 ms. */
+#define C1_SWITCH_FADE_SAMPLES     512
+
 /* One-time enable of the tile[1] core divider output path. MUST run on tile[1]. */
 void c1_tile1_clk_enable(void);