Its the same way. It seems as you are using the default Title field to determine if its music or movie.. and that is a text field. The created by field is Author - you can see the default names here http://blogs.msdn.com/b/michael_yeager/archive/2008/11/03/reference-list-for-internal-field-names.aspx
List<string> list = new List<string>();
Guid webID = SPContext.Current.Web.ID;
Guid siteID = SPContext.Current.Site.ID;
SPSecurity.RunWithElevatedPrivileges(delegate() // Code runs as the "SharePoint\system" user
{
using (SPSite site = new SPSite(siteID))
{
using (SPWeb web = site.AllWebs[webID])
{
SPList spList = web.Lists["CList"];
SPQuery query = new SPQuery();
query.Query = string.Concat(
"<Where><Eq>",
"<FieldRef Name='Title'/>",
"<Value Type='TEXT'>Movie</Value>",
"</Eq></Where>");
SPListItemCollection collListItems = spList.GetItems(query); // You need to use getitems to get specific items look here http://msdn.microsoft.com/en-us/library/ms457534.aspx
foreach (SPListItem item in collListItems)
{
list.Add(item["Author"].ToString()); // it's an internal field so you can use it
}
}
}
});