You would have to pass the parameter twice like:
SELECT UserArtistName,UserBandName, UserBusinessName, UserInfluences AS 'who' FROM users UNION SELECT AlbumTitle, AlbumTrack1, AlbumTrack2, AlbumTrack3, AlbumTrack4, AlbumTrack5, AlbumTrack6, AlbumTrack7, AlbumTrack8, AlbumTrack9, AlbumTrack10, AlbumTrack11, AlbumTrack12, AlbumTrack13, AlbumTrack14, AlbumTrack15, AlbumTrack16, AlbumTrack17, AlbumTrack18, AlbumTrack19, AlbumTrack20 AS 'what' FROM discography WHERE ('who' LIKE ? OR 'what' LIKE ?) OR UserGenreID = ? OR UserState = ?
$rsResults->bindParam("c", "".(isset($_POST['keyword'])?$_POST['keyword']:"") ."", "-1"); //paramKeywords
$rsResults->bindParam("c", "".(isset($_POST['keyword'])?$_POST['keyword']:"") ."", "-1"); //paramSecondKeywords
$rsResults->bindParam("i", "".(isset($_POST['genre'])?$_POST['genre']:"") ."", "-1"); //paramGenre
$rsResults->bindParam("s", "".(isset($_POST['state'])?$_POST['state']:"") ."", "-1"); //paramState