just an idea:
but maybe we could abstract some logic ?

private get($param, func){
 +		$this->response->setFormat( WikiaResponse::FORMAT_JSON );
 +
 +		$artist = $this->wg->Request->getVal( $param );
 +
 +		if( empty( $artist ) ) {
 +			throw new InvalidParameterApiException( $param );
 +		}
 +
 +		$results = func( $artist );
 +		$this->response->setVal( 'result', $results );
 +		$this->response->setCacheValidity( self::RESPONSE_CACHE_VALIDITY );
}

public function getArtist( ) {
get(self::PARAM_ARTIST, $this->lyricsApiHandler->getArtist);
 +	}

or maybe some magic funcition ? :)