Unity Android load local MP3 or WAV as AudioClip

I'm able to load audio using UnityWebRequestMultimedia.GetAudioClip in the Unity Editor with the following code but when I run it on Android I am unable to load any files from the user's device.

void Start() {
    audio = GetComponent<AudioSource>();
    string fullPath = Path.Combine("file://" + previewSong);
    StartCoroutine(GetAudioClip(fullPath));
}

IEnumerator GetAudioClip(string fullPath)
{
    using (var uwr = UnityWebRequestMultimedia.GetAudioClip(fullPath, AudioType.MPEG))
    {
        ((DownloadHandlerAudioClip)uwr.downloadHandler).streamAudio = true;

        yield return uwr.SendWebRequest();

        if (uwr.isNetworkError || uwr.isHttpError)
        {
            debugSongPath2.text = uwr.error;
            yield break;
        }

        DownloadHandlerAudioClip dlHandler = (DownloadHandlerAudioClip)uwr.downloadHandler;

        if (dlHandler.isDone)
        {
            audio.clip = dlHandler.audioClip;

            if (audio.clip != null)
            {
                audio.clip = DownloadHandlerAudioClip.GetContent(uwr);

                Debug.Log("Playing song using Audio Source!");
            }
            else
            {
                Debug.Log("Couldn't find a valid AudioClip.");
            }
        }
        else
        {
            Debug.Log("The download process is not completely finished.");
        }
    }
}

The errors I experience vary depending on how I form the start of the URL.

Path.Combine("file:/" + previewSong);
malformed URL

Path.Combine("file://" + previewSong); 
http:/1.1 404 not found

Path.Combine("file:///" + previewSong);
unknown error

Path.Combine("file:////" + previewSong);
unknown error

When I output the URLs on my phone they look correct. Here's an example path:

file:///storage/emulated/0/Music/Deorro/Deorro - Five Hours.mp3

I was previously loading audio from this URL successfully with WWW.GetAudioClip but that's obsolete. This leads me to believe the URL is correct. I've tried building with and without Development Mode. Not sure what else to try. I'd like to get this working with UnityWebRequestMultimedia but if there is an alternative, more effective way of loading local files I'm open to it.

from Unity Android load local MP3 or WAV as AudioClip