Benefits of the Hadith: (… The Prophet (peace and blessings be upon him) recited Surat al-Fath on his mount during his journey in the Year of the Conquest, and he modulated his voice in his recitation …).

The Shaykh : This was when the Prophet (peace and blessings be upon him) recited Surat al-Fath on his mount during the Conquest, fulfilling what Allah (Glorified and Exalted is He) had promised. He used to modulate his voice, meaning… the scholars said that this was because he was on his mount, and the mount was moving and swaying in its gait, so the voice followed it. This is because other hadiths have been reported indicating that he did not modulate his voice in his recitation. Modulation means repeating the letters. It is reported in al-Bukhari that he used to say that he would repeat the hamzah and repeat some of the letters. As I mentioned to you, it appears that this was due to the movement.
The student: ... .

The Shaykh : of the mount. As for when there was no movement, he did not modulate his voice.