"I heard Muhammad bin Hatib say: 'What differentiates between the lawful and the unlawful is the voice (singing).'" (Using translation from Nasāʾī 3370)
قَالَ رَسُولُ اللهِ ﷺ إِنَّ فَصْلَ مَا بَيْنَ الْحَلَالِ وَالْحَرَامِ الصَّوْتُ يَعْنِي الضَّرْبَ بِالدُّفِّ