In your object table;

public function findArtistBy(Query $query, array $options)
{
$artist = $options['search'];

return $query->where(['artist LIKE ' => $artist])
->orwhere(['title LIKE ' => $artist])
->contain(['Mp3files'])
->order(['title' => 'DESC']);
}

In your controller method;

$options['search']=$search;
$query=$this->Mp3filesTags->find('ArtistBy',$options);

$this->Flash->success(__('Search complete'));

$this->set('results', $query);
$this->set('count',$count);

So what does it do?
It will return the results where the artist field is like eg.”U2″ and where the title is like “U2”.
It also has an order clause in there and will contain the related records set “mp3files”.

Reference:
http://book.cakephp.org/3.0/en/orm/query-builder.html