It was the practice of the Prophet (peace and blessings be upon him):
"He (peace and blessings be upon him) would draw out his voice at length when reciting the Qur'an."
Hadith Referenceصحیح الجامع الصغیر / حرف الكاف / 5013
Hadith Gradingالألبانی:صحيح
Hadith Takhrij[حم ن هـ ك] عن أنس. خ: فضائل القرآن.