Powershell Output Help
In order to have it go to one file you have two options, and I think the first will get a little better performance than the second.

First you can simply add a parameter to the Export-Csv to append to the file. As long as the columns are consistent (the same) it should work with out issue.

$dt | Export-Csv music.csv -Encoding ascii -NoTypeInformation -Append


Second, pull the contents of the foreach loop into a variable and then output it all at one time to the Export-Csv. This will will mean it will pull all of the data into memory and then output it all to the file. It depends on how much data you are pulling out but this may add on some time for the execution of the script.

$results = 
foreach ($svr in get-content "demo.txt")
{
  $con = "server=MC1-PQ10X.RF.LILLY.COM\SQL01;database=mylilly_WSS_Content_INCTSK0014840;Integrated Security=sspi" 

  $cmd = "SELECT
Docs.DirName + '/' + Docs.LeafName AS 'Item Name',
DocVersions.UIVersion, 
(DocVersions.UIVersion/512) as Version_Label, DocVersions.Level, DocVersions.TimeCreated
FROM DocVersions FULL OUTER JOIN Docs ON Docs.Id = DocVersions.Id
--   INNER JOIN Webs On Docs.WebId = Webs.Id
--INNER JOIN Sites ON Webs.SiteId = SItes.Id
WHERE (DirName LIKE '%globalcontentrepository%')
AND (IsCurrentVersion = '0')
AND (DocVersions.Id IN ('$svr'))"

  $da = new-object System.Data.SqlClient.SqlDataAdapter ($cmd, $con)

  $dt = new-object System.Data.DataTable

  $da.fill($dt) |out-null

  $dt

 }

$results | Export-Csv music.csv -Encoding ascii -NoTypeInformation