When selecting new Repertoire to build your voice, one of the greatest secrets is to find MODERATE challenges. In other words, don't select a song that's too easy or a song that's too difficult. Many singers pick material that is far too challenging thinking "if only I can sing THIS song, then everything else will be easy". This is actually a big mistake. The voice is built fastest and freest when it grows in small, steady increments. Look for songs that are mostly within your range except for a few difficult passages that stretch you. Consider not just range, but also tessitura, length of notes and phrases, agility, musical difficulty, stylistic details, and emotional depth. In finding songs that are challenging yet still achievable, you'll feel happier about your voice and you'll also see it grow faster than ever!