Add Media Playlist Download link - response to https://www.damiencarbery.com/2017/02/add-download-link-to-wordpress-audio-player/#comment-2914

playlist-with-download-link.php

<?php
/*
Plugin Name: Add Media Playlist Download link
Plugin URI: https://wordpress.stackexchange.com/a/292952
Description: Adding a download link to native WordPress playlist - StackExchange answer
Author: Blix
Version: 0.1
*/

// This code is an answer to
// https://wordpress.stackexchange.com/questions/292585/adding-a-download-link-to-native-wordpress-playlist
// Answer: https://wordpress.stackexchange.com/a/292952

add_action( 'wp_head', 'dcwd_change_playlist' );
function dcwd_change_playlist() {
?>
<script type="text/html" id="tmpl-wp-playlist-current-item">
    <# if ( data.image ) { #>
    <img src="{{ data.thumb.src }}"/>
    <# } #>
    <div class="wp-playlist-caption">
            <span class="wp-playlist-item-meta wp-playlist-item-title">{{ data.title }}</span>
            <# if ( data.meta.album ) { #><span class="wp-playlist-item-meta wp-playlist-item-album">{{ data.meta.album }}</span><# } #>
            <# if ( data.meta.artist ) { #><span class="wp-playlist-item-meta wp-playlist-item-artist">{{ data.meta.artist }}</span><# } #>
    </div>

</script>
<script type="text/html" id="tmpl-wp-playlist-item">
    <div class="wp-playlist-item">
            <a class="wp-playlist-caption" href="{{ data.src }}">
                    {{ data.index ? ( data.index + '. ' ) : '' }}
                    <# if ( data.caption ) { #>
                            {{ data.caption }}
                    <# } else { #>
                            <span class="wp-playlist-item-title">{{{ data.title }}}</span>
                            <# if ( data.artists && data.meta.artist ) { #>
                            <span class="wp-playlist-item-artist"> — {{ data.meta.artist }}</span>
                            <# } #>
                    <# } #>
            </a>
            <# if ( data.meta.length_formatted ) { #>
            <div class="wp-playlist-item-length">{{ data.meta.length_formatted }}</div>
            <# } #>             
    </div>

    <!-- BEGIN CHANGES -->
       <a href="{{ data.src }}" class="wpse-download" download=""><i class="fa fa-download" title="Download" aria-hidden="true"></i></a>
    <!-- END CHANGES -->
</script>
<!--<style>
/*playlist title - more to right*/
.wp-playlist-item-title {
    padding-left:25px
}

/*download link styles - move within playlist & to left of playlist title*/

.wpse-download {
    margin-top: -22px;
    padding-left:5px;
    position: absolute;
}

/*change color of icon*/
.wpse-download {
 color:white!important;
}

/*change hover / active state of download icon*/
.wpse-download:hover, .wpse-download:visited
{
 color:#aaa!important;
}
</style>-->
<?php
}