How can I speed up an sql query that round trips between two tables
It's more or less like this...

SELECT m.*
     , COUNT(p.sid) frequency
  FROM music m
  JOIN plays p
    ON p.sid = m.sid
 WHERE p.time &gt; NOW() - INTERVAL 3 DAY 
   AND p.sid != '' 
   AND m.perms != 'c' 
 GROUP 
    BY m.sid
 ORDER 
    BY frequency DESC
 LIMIT 50