class Media {
    public int id {get;set;}
    public string mediatype {get;set;}
}

class Song : Media {
    public string album {get;set;}
}

class Movie : Media {
    public string name {get;set;}
}

create type AllMedia as table
(
    id int,
    mediatype nvarchar(50),
    album nvarchar(50),
    name nvarchar(50)
)

class MediaTable{
    public int id {get;set;}
    public string mediatype {get;set;}
    public string album {get;set;}
    public string name {get;set;}

    public static List<MediaTable> ToMediaTable<T>(List<T> media){
        ...
    }
}