diff --git a/src/Simplifiers/SimpleAlbum.php b/src/Simplifiers/SimpleAlbum.php
index ec22fbb..8b6709f 100644
--- a/src/Simplifiers/SimpleAlbum.php
+++ b/src/Simplifiers/SimpleAlbum.php
@@ -113,7 +113,7 @@ public function __construct($ern) {
 		// Find release of type MainRelease from this ERN
 		foreach ($this->ern->getReleaseList()->getRelease() as $release) {
 			foreach ($release->getReleaseType() as $type) {
-				if (in_array(strtolower($type->value()), ["album", "classicalalbum"])) {
+				if (in_array(strtolower($type->value()), ["album", "classicalalbum", "single"])) {
 					$this->ddexReleaseAlbum = $release;
 				} else {
 					$this->trackReleasesByReference[$release->getReleaseReference()[0]] = $release;
@@ -523,5 +523,50 @@ public function getCLineText(): ?string {
 			return null;
 		}
 	}
+  
+  /**
+   * Assumption: there is only one ReleaseId
+   * 
+   * @return string|null
+   */
+  public function getGrid(): ?string {
+    try {
+			return $this->ddexReleaseAlbum->getReleaseId()[0]->getGRid();
+		} catch (Throwable $ex) {
+			return null;
+		} catch (Exception $ex) {
+			return null;
+		}
+  }
+  
+  /**
+   * Assumption: there is only one ReleaseId
+   * 
+   * @return string|null
+   */
+  public function getIcpn(): ?string {
+    try {
+			return $this->ddexReleaseAlbum->getReleaseId()[0]->getICPN();
+		} catch (Throwable $ex) {
+			return null;
+		} catch (Exception $ex) {
+			return null;
+		}
+  }
+  
+  /**
+   * Assumption: there is only one ReleaseId
+   * 
+   * @return string|null
+   */
+  public function getCatalogNumber(): ?string {
+    try {
+			return $this->ddexReleaseAlbum->getReleaseId()[0]->getCatalogNumber();
+		} catch (Throwable $ex) {
+			return null;
+		} catch (Exception $ex) {
+			return null;
+		}
+  }
 
 }
diff --git a/src/Simplifiers/SimpleTrack.php b/src/Simplifiers/SimpleTrack.php
index a0805a2..bb3906e 100644
--- a/src/Simplifiers/SimpleTrack.php
+++ b/src/Simplifiers/SimpleTrack.php
@@ -242,7 +242,7 @@ public function getDurationInSeconds(): ?int {
 	 * 
 	 * @return SimpleArtist[]
 	 */
-	private function getDisplayArtists() {
+	public function getDisplayArtists() {
 		$artists = [];
 		
 		foreach ($this->ddexDetails->getDisplayArtist() as $artist) {
@@ -263,7 +263,7 @@ private function getDisplayArtists() {
 	 * 
 	 * @return SimpleArtist
 	 */
-	private function getArtistsFromResourceContributors() {
+	public function getArtistsFromResourceContributors() {
 		$artists = [];
 		
 		foreach ($this->ddexDetails->getResourceContributor() as $artist) {
@@ -284,7 +284,7 @@ private function getArtistsFromResourceContributors() {
 	 * 
 	 * @return SimpleArtist
 	 */
-	private function getArtistsFromIndirectResourceContributors() {
+	public function getArtistsFromIndirectResourceContributors() {
 		$artists = [];
 		
 		foreach ($this->ddexDetails->getIndirectResourceContributor() as $artist) {
@@ -307,7 +307,7 @@ private function getArtistsFromIndirectResourceContributors() {
 	 * 
 	 * Ignores sequence numbering. Keep the order as written in the XML.
 	 * 
-	 * @return SimpleArtist
+	 * @return SimpleArtist[]
 	 */
 	public function getArtists() {
 		// Display artists