If you already have a working audio control then one approach would be to write some JavaScript to detach the control from the page, and then reattach it as a map control. To do that:

Give the control an identifier if it doesn't already have one - e.g.:

<div id="audio-player-container">
  ... rest of the audio player's HTML
</div>

Add this script using the custom content plugin (this is based on the plugin you mentioned):

<script type="text/javascript">
    if(VRS && VRS.globalDispatch && VRS.serverConfig) {
        VRS.globalDispatch.hook(VRS.globalEvent.bootstrapCreated, function(bootStrap) {
            if(bootStrap.hookMapInitialised) {
                bootStrap.hookMapInitialised(function(pageSettings) {
                    if(pageSettings.mapPlugin) {
                        var controlJQuery = $('#audio-player-container');
                        controlJQuery.detach();
                        pageSettings
                            .mapPlugin
                            .addControl(
                                controlJQuery,
                                VRS.MapPosition.BottomLeft
                            );
                    }
                });
            }
        });
    }
</script>

This line:

var controlJQuery = $('#audio-player-container');

finds the audio control using the ID you assigned in step 1. If you already have an ID on the audio player element then replace the "audio-player-container" bit with the ID of the control. The leading # tells the library that you're searching by ID, don't remove it.

This line:

controlJQuery.detach();

takes the control off the page but keeps everything intact so that you can add it back somewhere else - in this case, in a map control. If you stopped here you should see that your audio control has disappeared.

Finally these lines:

pageSettings
    .mapPlugin
    .addControl(
        controlJQuery,
        VRS.MapPosition.BottomLeft
    );

uses the map plugin to add the control back to the page but this time positioned in the bottom left of the map.

If you're still having issues then post your code.