diff --git a/src/components/library-item/library-item.css b/src/components/library-item/library-item.css
index e25c478d2..c702492f8 100644
--- a/src/components/library-item/library-item.css
+++ b/src/components/library-item/library-item.css
@@ -27,12 +27,6 @@
     transform: scale(1.02, 1.02);
 }
 
-.library-item.is-selected {
-    border-width: 2px;
-    border-color: #1dacf4;
-    transition: 0.25s ease-out;
-}
-
 .library-item-image-container {
     height: 100px;
 }
@@ -47,12 +41,12 @@
     margin: 0.25rem 0;
     text-align: center;
 
-    /* 
+    /*
         For truncating overflowing text gracefully
         Min-width is for a bug: https://css-tricks.com/flexbox-truncated-text
     */
     overflow: hidden;
     text-overflow: ellipsis;
     white-space: nowrap;
-    min-width: 0; 
+    min-width: 0;
 }
diff --git a/src/components/library-item/library-item.jsx b/src/components/library-item/library-item.jsx
index 31e722b0e..8e113c9be 100644
--- a/src/components/library-item/library-item.jsx
+++ b/src/components/library-item/library-item.jsx
@@ -1,4 +1,3 @@
-const classNames = require('classnames');
 const bindAll = require('lodash.bindall');
 const PropTypes = require('prop-types');
 const React = require('react');
@@ -9,20 +8,29 @@ const styles = require('./library-item.css');
 class LibraryItem extends React.Component {
     constructor (props) {
         super(props);
-        bindAll(this, ['handleClick']);
+        bindAll(this, [
+            'handleClick',
+            'handleMouseEnter',
+            'handleMouseLeave'
+        ]);
     }
     handleClick (e) {
         this.props.onSelect(this.props.id);
         e.preventDefault();
     }
+    handleMouseEnter () {
+        this.props.onMouseEnter(this.props.id);
+    }
+    handleMouseLeave () {
+        this.props.onMouseLeave(this.props.id);
+    }
     render () {
         return (
             <Box
-                className={classNames({
-                    [styles.libraryItem]: true,
-                    [styles.isSelected]: this.props.selected
-                })}
+                className={styles.libraryItem}
                 onClick={this.handleClick}
+                onMouseEnter={this.handleMouseEnter}
+                onMouseLeave={this.handleMouseLeave}
             >
                 <Box className={styles.libraryItemImageContainer}>
                     <img
@@ -40,8 +48,9 @@ LibraryItem.propTypes = {
     iconURL: PropTypes.string.isRequired,
     id: PropTypes.number.isRequired,
     name: PropTypes.string.isRequired,
-    onSelect: PropTypes.func.isRequired,
-    selected: PropTypes.bool.isRequired
+    onMouseEnter: PropTypes.func.isRequired,
+    onMouseLeave: PropTypes.func.isRequired,
+    onSelect: PropTypes.func.isRequired
 };
 
 module.exports = LibraryItem;
diff --git a/src/components/library/library.jsx b/src/components/library/library.jsx
index 16327c10c..71b29ff61 100644
--- a/src/components/library/library.jsx
+++ b/src/components/library/library.jsx
@@ -10,20 +10,21 @@ const styles = require('./library.css');
 class LibraryComponent extends React.Component {
     constructor (props) {
         super(props);
-        bindAll(this, ['handleSelect']);
-        this.state = {selectedItem: null};
+        bindAll(this, [
+            'handleSelect',
+            'handleMouseEnter',
+            'handleMouseLeave'
+        ]);
     }
     handleSelect (id) {
-        if (this.state.selectedItem === id) {
-            // Double select: select as the library's value.
-            this.props.onRequestClose();
-            this.props.onItemSelected(this.props.data[id]);
-        } else {
-            if (this.props.onItemChosen) {
-                this.props.onItemChosen(this.props.data[id]);
-            }
-        }
-        this.setState({selectedItem: id});
+        this.props.onRequestClose();
+        this.props.onItemSelected(this.props.data[id]);
+    }
+    handleMouseEnter (id) {
+        if (this.props.onItemMouseEnter) this.props.onItemMouseEnter(this.props.data[id]);
+    }
+    handleMouseLeave (id) {
+        if (this.props.onItemMouseLeave) this.props.onItemMouseLeave(this.props.data[id]);
     }
     render () {
         if (!this.props.visible) return null;
@@ -45,7 +46,8 @@ class LibraryComponent extends React.Component {
                                 id={itemId}
                                 key={`item_${itemId}`}
                                 name={dataItem.name}
-                                selected={this.state.selectedItem === itemId}
+                                onMouseEnter={this.handleMouseEnter}
+                                onMouseLeave={this.handleMouseLeave}
                                 onSelect={this.handleSelect}
                             />
                         );
@@ -67,7 +69,8 @@ LibraryComponent.propTypes = {
         })
         /* eslint-enable react/no-unused-prop-types, lines-around-comment */
     ),
-    onItemChosen: PropTypes.func,
+    onItemMouseEnter: PropTypes.func,
+    onItemMouseLeave: PropTypes.func,
     onItemSelected: PropTypes.func,
     onRequestClose: PropTypes.func,
     title: PropTypes.string.isRequired,
diff --git a/src/containers/backdrop-library.jsx b/src/containers/backdrop-library.jsx
index b19921b4c..62e9cd473 100644
--- a/src/containers/backdrop-library.jsx
+++ b/src/containers/backdrop-library.jsx
@@ -4,7 +4,7 @@ const React = require('react');
 const VM = require('scratch-vm');
 
 const backdropLibraryContent = require('../lib/libraries/backdrops.json');
-const LibaryComponent = require('../components/library/library.jsx');
+const LibraryComponent = require('../components/library/library.jsx');
 
 
 class BackdropLibrary extends React.Component {
@@ -26,7 +26,7 @@ class BackdropLibrary extends React.Component {
     }
     render () {
         return (
-            <LibaryComponent
+            <LibraryComponent
                 data={backdropLibraryContent}
                 title="Backdrop Library"
                 visible={this.props.visible}
diff --git a/src/containers/costume-library.jsx b/src/containers/costume-library.jsx
index 1fea39a2d..d0a004ba6 100644
--- a/src/containers/costume-library.jsx
+++ b/src/containers/costume-library.jsx
@@ -4,7 +4,7 @@ const React = require('react');
 const VM = require('scratch-vm');
 
 const costumeLibraryContent = require('../lib/libraries/costumes.json');
-const LibaryComponent = require('../components/library/library.jsx');
+const LibraryComponent = require('../components/library/library.jsx');
 
 
 class CostumeLibrary extends React.Component {
@@ -26,7 +26,7 @@ class CostumeLibrary extends React.Component {
     }
     render () {
         return (
-            <LibaryComponent
+            <LibraryComponent
                 data={costumeLibraryContent}
                 title="Costume Library"
                 visible={this.props.visible}
diff --git a/src/containers/sound-library.jsx b/src/containers/sound-library.jsx
index d478d141a..53aa6bde0 100644
--- a/src/containers/sound-library.jsx
+++ b/src/containers/sound-library.jsx
@@ -3,7 +3,7 @@ const PropTypes = require('prop-types');
 const React = require('react');
 const VM = require('scratch-vm');
 const AudioEngine = require('scratch-audio');
-const LibaryComponent = require('../components/library/library.jsx');
+const LibraryComponent = require('../components/library/library.jsx');
 
 const soundIcon = require('../components/asset-panel/icon--sound.svg');
 
@@ -14,14 +14,19 @@ class SoundLibrary extends React.Component {
         super(props);
         bindAll(this, [
             'handleItemSelected',
-            'handleItemChosen'
+            'handleItemMouseEnter',
+            'handleItemMouseLeave'
         ]);
     }
     componentDidMount () {
         this.audioEngine = new AudioEngine();
         this.player = this.audioEngine.createPlayer();
     }
-    handleItemChosen (soundItem) {
+    componentWillReceiveProps (newProps) {
+        // Stop playing sounds if the library closes without a mouseleave (e.g. by using the escape key)
+        if (this.player && !newProps.visible) this.player.stopAllSounds();
+    }
+    handleItemMouseEnter (soundItem) {
         const md5ext = soundItem._md5;
         const idParts = md5ext.split('.');
         const md5 = idParts[0];
@@ -39,6 +44,9 @@ class SoundLibrary extends React.Component {
             this.player.playSound(soundItem._md5);
         });
     }
+    handleItemMouseLeave () {
+        this.player.stopAllSounds();
+    }
     handleItemSelected (soundItem) {
         const vmSound = {
             format: soundItem.format,
@@ -64,11 +72,12 @@ class SoundLibrary extends React.Component {
         });
 
         return (
-            <LibaryComponent
+            <LibraryComponent
                 data={soundLibraryThumbnailData}
                 title="Sound Library"
                 visible={this.props.visible}
-                onItemChosen={this.handleItemChosen}
+                onItemMouseEnter={this.handleItemMouseEnter}
+                onItemMouseLeave={this.handleItemMouseLeave}
                 onItemSelected={this.handleItemSelected}
                 onRequestClose={this.props.onRequestClose}
             />
diff --git a/src/containers/sprite-library.jsx b/src/containers/sprite-library.jsx
index c08748eb2..0a1bcaa3e 100644
--- a/src/containers/sprite-library.jsx
+++ b/src/containers/sprite-library.jsx
@@ -5,7 +5,7 @@ const VM = require('scratch-vm');
 
 const spriteLibraryContent = require('../lib/libraries/sprites.json');
 
-const LibaryComponent = require('../components/library/library.jsx');
+const LibraryComponent = require('../components/library/library.jsx');
 
 class SpriteLibrary extends React.Component {
     constructor (props) {
@@ -19,7 +19,7 @@ class SpriteLibrary extends React.Component {
     }
     render () {
         return (
-            <LibaryComponent
+            <LibraryComponent
                 data={spriteLibraryContent}
                 title="Sprite Library"
                 visible={this.props.visible}