Does a Muslim sin if he downloads chapters from the Holy Quran onto his phone, if the phone classifies them as a "song" and labels the reciter as an "artist"?

If it is possible to change the names of the audio clips of the Qur'an to avoid imitating the people of disobedience, then do so. Otherwise, continue; what the device does by naming them something other than their [actual] name does not harm you.

The naming of a reciter of the Qur'an as "artist" can be justified because "art" means a type or category of things, and tajwid is an art. Similarly, "song" can refer to the audio clip, but not to the Qur'an itself; for singing (ghina’) in the Arabic language is a sound that delights the listener. This is supported by the hadith: "Allah has not listened to anything as He has listened to a Prophet beautifying his voice when reciting the Qur'an," meaning making his voice beautiful with it.

As for naming the Qur'an itself "a song," this is not permissible. The Qur'an is the speech of Allah and His attribute, and the description of Allah's attributes is tawqifi (restricted to what is revealed).

For this reason, the Prophet, peace and blessings be upon him, described the voice of Abu Musa as a "flute" due to its beauty, but he did not describe the Qur'an itself as such.