Belting out is a phrase that is commonly used to describe someone singing loudly and with great enthusiasm. However, there are plenty of alternative words and phrases that can be used to convey a similar meaning. For instance, one could describe a singer as 'crooning,' 'warbling,' 'serenading,' or 'trilling.' Other synonyms for 'belting out' might include 'singing with gusto,' 'letting loose,' 'unleashing,' or 'exuding passion.' These words and phrases can help add variety to your writing or conversation, while also conveying the same sense of enthusiasm and energy that comes with singing loudly and confidently.