How to dynamically add OR operator to WHERE clause in LINQ

You can use the PredicateBuilder class:

var searchPredicate = PredicateBuilder.False<Songs>();

foreach(string str in strArray)
{
   var closureVariable = str; // See the link below for the reason
   searchPredicate = 
     searchPredicate.Or(SongsVar => SongsVar.Tags.Contains(closureVariable));
}

var allSongMatches = db.Songs.Where(searchPredicate);

LinqToSql strange behaviour