Billboard staffers look back on 2019 gems from Ozuna, Nilufer Yanya, Aly &amp; AJ, Sada Baby, Aldous Harding and Pink Sweat$.<hr><p style='color:grey; font-size:0.75em;'> Hosted on Acast. See <a style='color:grey;' target='_blank' rel='noopener noreferrer' href='https://acast.com/privacy'>acast.com/privacy</a> for more information.</p>