diff --git a/.epub/example/OEBPS/scripts/ipub.js b/.epub/example/OEBPS/scripts/ipub.js
index f70a681..b8a8f01 100644
--- a/.epub/example/OEBPS/scripts/ipub.js
+++ b/.epub/example/OEBPS/scripts/ipub.js
@@ -21,6 +21,151 @@ class IPUBElement extends HTMLElement {
   }
 }
 
+class IPUBAudio extends IPUBElement {
+  static elementName = "ipub-audio";
+
+  /**
+   * @param {boolean} [forced=false]
+   * @throws {Error}
+   * @returns {Promise<void>}
+   */
+  play(forced = false) {
+    if (!this.#audioElement.readyState > HTMLMediaElement.HAVE_CURRENT_DATA) {
+      throw new Error("IPUBAudio: audio is not ready");
+    }
+    if (forced) {
+      this.setAttribute("forced", "true");
+    }
+    return this.#audioElement.play();
+  }
+
+  /**
+   * @param {boolean} [forced=false]
+   */
+  pause(forced = false) {
+    if (forced) {
+      this.setAttribute("forced", "true");
+    }
+    this.#audioElement.pause();
+  }
+
+  /**
+   * @param {boolean} state
+   */
+  setLoop(state) {
+    this.#audioElement.loop = state;
+  }
+
+  /**
+   * @returns {boolean}
+   */
+  getLoop() {
+    return this.#audioElement.loop;
+  }
+
+  connectedCallback() {
+    super.connectedCallback();
+
+    const audio = this.querySelector("audio");
+    if (!audio) {
+      console.error("IPUBAudio: Missing child <audio> element");
+      return;
+    }
+
+    this.#audioElement = audio;
+  }
+
+  /**
+   * @private
+   * @type {HTMLAudioElement}
+   */
+  #audioElement;
+
+  /**
+   * @param {number} volume
+   * @param {Object} options
+   * @param {number} [options.fadetime=0]
+   * @param {() => void} [options.onfinish=() => {}]
+   */
+  setVolume(volume, { fadetimeMS = 0, onFinishFade = () => {} } = {}) {
+    if (fadetimeMS === 0) {
+      this.#audioElement.volume = volume / 100;
+      return;
+    }
+
+    if (this.#isFading) {
+      return;
+    }
+
+    this.#onFinishFade = onFinishFade;
+
+    const diff = volume - this.#audioElement.volume * 100;
+    const ticks = diff < 0 ? Math.abs(diff) : diff;
+    let tick = 0;
+
+    const interval = fadetimeMS / ticks;
+
+    this.#isFading = true;
+    this.#fadeTask = setInterval(() => {
+      tick++;
+
+      const cancel = () => {
+        this.#isFading = false;
+        if (onFinishFade) {
+          onFinishFade();
+        }
+        clearInterval(this.#fadeTask);
+        this.#onFinishFade = null;
+      };
+
+      if (!this.#audioElement) {
+        cancel();
+        console.error("IPUBAudio: Missing child <audio> element");
+        return;
+      }
+
+      if (ticks < tick) {
+        cancel();
+        return;
+      }
+
+      if (volume === this.getVolume()) {
+        cancel();
+        return;
+      }
+
+      if (diff === 0) {
+        cancel();
+        return;
+      }
+
+      const nvol =
+        (diff > 0
+          ? Math.ceil(this.#audioElement.volume * 100 + 1)
+          : Math.floor(this.#audioElement.volume * 100 - 1)) / 100;
+
+      if (nvol > 1 || nvol < 0) {
+        cancel();
+        return;
+      }
+
+      this.#audioElement.volume = nvol;
+    }, interval);
+  }
+
+  /**
+   * @returns {number}
+   */
+  getVolume() {
+    return Math.floor((this.#audioElement?.volume ?? 0) * 100);
+  }
+
+  #isFading = false;
+  #fadeTask = 0;
+  /** @type {() => void | null} */
+  #onFinishFade = null;
+}
+
 class IPUBBackground extends IPUBElement {
   static elementName = "ipub-background";
   static observedAttributes = ["nofade"].concat(super.observedAttributes);
@@ -182,9 +327,11 @@ class IPUBBody extends IPUBElement {
 
   static defineContentElements() {
     for (const e of [
+      IPUBAudio,
       IPUBBackground,
       IPUBImage,
       IPUBInteraction,
+      IPUBSoundtrack,
     ]) {
       console.info(`IPUBBody: Defining custom element <${e.elementName}>`);
       globalThis.customElements.define(e.elementName, e);
@@ -288,14 +435,132 @@ class IPUBInteraction extends IPUBElement {
   static elementName = "ipub-interaction";
 }
 
+class IPUBSoundtrack extends IPUBElement {
+  static elementName = "ipub-soundtrack";
+
+  // TODO: Toggle automatic soundtrack playing
+
+  /**
+   * @private
+   */
+  static #player = setInterval(() => {
+    const last = Array.from(this.#onScreenStack).pop();
+    if (!last) {
+      // TODO: Fallback to previous soundtrack if there's no audio
+      return;
+    }
+
+    // TODO: Get siblings based by group OR parent
+    /** @type {NodeListOf<IPUBSoundtrack> | undefined} */
+    const siblings = last.parentElement?.querySelectorAll(
+      IPUBSoundtrack.elementName,
+    );
+
+    try {
+      if (siblings) {
+        siblings.forEach((el) => {
+          if (el !== last) {
+            el.fadeOut();
+          }
+        });
+      }
+      last.fadeIn();
+    } catch (e) {
+      // TODO: Fallback to previous soundtrack on error
+      console.error(
+        `IPUBSoundtrack: error while trying to play audio, error: ${e}`,
+        {
+          error: e,
+          audio: audio,
+        },
+      );
+    }
+  }, 1000);
+
+  /**
+   * @private
+   */
+  static #observer = (() => {
+    return new IntersectionObserver((entries) => {
+      for (const { intersectionRatio, target, time } of entries) {
+        /** @type {IPUBSoundtrack} */
+        const soundtrack = target;
+
+        if (intersectionRatio > 0) {
+          console.debug(`${soundtrack.id} is on screen at ${time}`, soundtrack);
+          this.#onScreenStack.add(soundtrack);
+        } else {
+          console.debug(
+            `${soundtrack.id} is not on screen ${time}`,
+            soundtrack,
+          );
+          this.#onScreenStack.delete(soundtrack);
+        }
       }
     });
+  })();
 
+  /**
+   * @private
+   * @type {Set<IPUBSoundtrack>}
+   */
+  static #onScreenStack = new Set();
 
-
-
+  /**
+   * @throws {Error}
+   */
+  fadeIn() {
+    /** @type {IPUBAudio | undefined} */
+    const audio = this.querySelector(IPUBAudio.elementName);
+    if (!audio) {
+      throw new Error("IPUBSoundtrack.fadeIn: missing audio element");
     }
 
+    // TODO: Global volume settings
+
+    audio.play();
+    audio.setVolume(10, { fadetimeMS: IPUBSoundtrack.FADE_TIME_MS });
+  }
+
+  /**
+   * @throws {Error}
+   */
+  fadeOut() {
+    /** @type {IPUBAudio | undefined} */
+    const audio = this.querySelector(IPUBAudio.elementName);
+    if (!audio) {
+      throw new Error("IPUBSoundtrack.fadeIn: missing audio element");
+    }
+
+    audio.setVolume(0, {
+      fadetimeMS: IPUBSoundtrack.FADE_TIME_MS,
+      onFinishFade: () => {
+        audio.pause();
+      },
+    });
+  }
+
+  /** @type {Readonly<number>} */
+  static FADE_TIME_MS = 1000 * 3;
+
+  connectedCallback() {
+    super.connectedCallback();
+
+    /** @type {IPUBAudio | undefined} */
+    const audio = this.querySelector(IPUBAudio.elementName);
+    if (audio) {
+      audio.setVolume(0);
+    } else {
+      console.error("IPUBSoundtrack: missing audio element");
+      return;
+    }
+
+    IPUBSoundtrack.#observer.observe(this);
+  }
+
+  // TODO(guz013): Handle if element is moved, it's group should be updated
+}
+
 /**
  * @param {HTMLElement} el
  * @param {string} tagName
diff --git a/.epub/example/OEBPS/sections/section0001.xhtml b/.epub/example/OEBPS/sections/section0001.xhtml
index f4c09e3..2b2eb5e 100644
--- a/.epub/example/OEBPS/sections/section0001.xhtml
+++ b/.epub/example/OEBPS/sections/section0001.xhtml
@@ -27,6 +27,21 @@
         <ipub-background id="background0001">
           <img src="../images/background0001.jpg" width="100" height="100" />
         </ipub-background>
+        <ipub-soundtrack style="--ipub-color:cyan">
+          <!-- TODO: Search on how to make this more accessible, more semantic as using <details> -->
+          <figure>
+            <label>
+              <input type="checkbox" />
+              <figcaption>Soundtrack 1</figcaption>
+            </label>
+            <ipub-audio>
+              <audio controls="true" volume="0" controlslist="nofullscreen"
+              disableremoteplayback="">
+                <source src="../audios/track1.webm" />
+              </audio>
+            </ipub-audio>
+          </figure>
+        </ipub-soundtrack>
         <ipub-image>
           <img src="../images/image0001.png" />
           <ipub-interaction style="--ipub-y:88.5%;--ipub-x:6%" circle="">
@@ -41,6 +56,20 @@
         <ipub-image>
           <img src="../images/image0002.png" />
         </ipub-image>
+        <ipub-soundtrack style="--ipub-color:green;">
+          <figure>
+            <label>
+              <input type="checkbox" />
+              <figcaption>Soundtrack 2</figcaption>
+            </label>
+            <ipub-audio>
+              <audio controls="true" volume="0" controlslist="nofullscreen"
+              disableremoteplayback="">
+                <source src="../audios/track2.webm" />
+              </audio>
+            </ipub-audio>
+          </figure>
+        </ipub-soundtrack>
         <ipub-background id="background0002">
           <picture>
             <img src="../images/background0002.jpg" />
@@ -60,6 +89,20 @@
         <ipub-image>
           <img src="../images/image0002.png" />
         </ipub-image>
+        <ipub-soundtrack style="--ipub-color:yellow;">
+          <figure>
+            <label>
+              <input type="checkbox" />
+              <figcaption>Soundtrack 3</figcaption>
+            </label>
+            <ipub-audio>
+              <audio controls="true" volume="0" controlslist="nofullscreen"
+              disableremoteplayback="">
+                <source src="../audios/track3.webm" />
+              </audio>
+            </ipub-audio>
+          </figure>
+        </ipub-soundtrack>
         <ipub-image>
           <img src="../images/image0003.png" />
         </ipub-image>