The Prophet (ﷺ) Hearing Bells During Revelation
In this Hadith, the Prophet mentioned that sometimes, the descent of the archangel Gabriel on him with the divine revelation inwardly sounds "like the ringing of a bell":
Sometimes it (i.e., divine revelation) comes down like the ringing of a bell, and this is the hardest of all (forms of revelation) for me. This state then passes after I have grasped what he has said.
Bukhari 2
Yet in other Hadiths, the Prophet said that angels don't accompany bell sounds:
Angels accompany not the travellers who have with them a dog nor a bell.
Muslim 2113a
The angels do not accompany the fellow travelers who have a dog or bell with them.
Abu Dawud 2555
The angels do not accompany groups of people who have small bells with them.
Nasa'i 5220/5221
The angels do not enter a house in which there is a small bell or a bell, and the angels do not accompany groups of people who have bells with them.
Nasa'i 5222
Quoting these narrations, some may imply that the revelation was transmitted by someone other than Gabriel, since after all, the bell is the musical instrument of Satan:
The bell is the musical instrument of Satan.
Muslim 2114
This reasoning, however, is flawed. The Prophet said that the hardest form of revelation comes down to him "like the ringing of a bell," meaning it comes down in a way similar to the ringing of a bell, and this doesn't refer to the instrument of a bell but rather the physical experience of the revelation, something completely different to musical sounds.
This is a simile, and in similes it's not necessary that the two ends of the comparison are identical in all characteristics; it's enough that they share one characteristic, which is in this case the strength of the sound of revelation. The simile in the Hadith is to represent what is intangible by mentioning something the audiences are familiar with in order to be easily understood.
This is a common grammar rule; when someone is said to be "like a lion," that is not to say that they have manes, claws and fangs, and that they live in the jungle, but that they share the characteristic of strength or courage with a lion. Examples of similes like these are employed in other Hadiths as well:
Verily, the faith would recede to Medina just as the serpent crawls back into its hole.
Muslim 147
Is the Prophet here saying that "faith" is like a "snake" in every aspect? No, this is just likening faith to a snake in a single characteristic (i.e., crawling), and not in every aspect; that's not a similitude of its essence, but rather a similitude between action to demonstrate a comparison easy for people to understand, because if we took that in literally every aspect, that would explicitly contradict the many other Hadiths enjoining the killing of snakes.
Moreover, and to further explain the simile employed here, the Hadith isn't actually in reference to the bell itself (i.e., a musical instrument where its tones are manipulated using different strengths of striking in order to produce a rhythm composed of different sounds of different frequencies), but rather is described as the similitude of vibrations caused due to the material of the bell (which is described as a piece of metal); the described sound is a strong sound that resembles that of when a piece of iron is struck, therefore, the likening is to do with the single sound and vibration caused when a piece of metal is struck, and not to do with any instrumental modality or producing a musical rhythm. The wisdom behind the strength of the sound is that the revelation would command his full attention and he would not hear anything else while revelation was being revealed to him.
The bell however, being an instrument of Satan, is in reference to the physical musical instruments which people play, since these are means by which hearts of the people can be strayed from the remembrance of Allah; say that for instance, modern technology used to play music (e.g., music players and .mp3 files with music) may also be referred to as "instruments of Satan," in this case. Therefore, we can safely conclude that the musical instrument the Prophet referred to as a tool of Satan and what he heard during revelation are two completely different things.