|---------------------|------------------|------------------|
|      Title          |         ID       |      Version     |
|---------------------|------------------|------------------|
|   songnumber1       |         34       |    original      |
|---------------------|------------------|------------------|
|   songnumber2       |         35       |      remix       |
|---------------------|------------------|------------------|
|   songnumber3       |         36       |      remix       |
|---------------------|------------------|------------------|

|---------------------|------------------|------------------|
|         ID          |      remix       |      original    |
|---------------------|------------------|------------------|
|         1           |        35        |        34        |
|---------------------|------------------|------------------|
|         2           |        36        |        36        |
|---------------------|------------------|------------------|

SELECT * FROM reference
         INNER JOIN songs ON reference.remix = songs.id OR
reference.original = songs.id
         WHERE reference.original = '$id' OR reference.remix = '$id'

SELECT
  C.currently_playing,
  GROUP_CONCAT(DISTINCT IF(C.currently_playing=C.id,C.title,null)) current_song_title,
  GROUP_CONCAT(DISTINCT IF(C.version='original',C.id,null)) orignial_song_id,
  GROUP_CONCAT(DISTINCT IF(C.version='original',C.title,null)) orignial_song_title,
  GROUP_CONCAT(DISTINCT IF(C.version='remix',C.id,null)) related_remix_ids,
  GROUP_CONCAT(DISTINCT IF(C.version='remix',C.title,null)) related_remix_titles
FROM
  (SELECT 35 AS currently_playing, A.*
   FROM Songs   A
   RIGHT JOIN (SELECT * FROM `references` WHERE remix=35 or original=35) B
   ON A.id IN (B.original,B.remix)) C
GROUP BY C.currently_playing;

SELECT * FROM reference r
INNER JOIN songs a ON r.remix = a.ID
INNER JOIN songs b ON r.original = b.ID
WHERE r.remix = 35

SELECT * FROM reference r
INNER JOIN Songs a ON r.remix = a.ID
WHERE r.remix = 35
UNION
SELECT * FROM reference r
INNER JOIN Songs b ON r.original = b.ID
WHERE r.remix = 35