What is the secret behind the permissibility of the drum (duff) to the exclusion of other musical instruments?

The daff (tambourine) is an exception to the general prohibition of musical instruments. The difference between it and the drum is that the daff has one side, while the drum has two, which makes the drum's sound and melody stronger than the daff's, and its reverberation more rhythmic. The drum is a forbidden musical instrument, as are flutes, stringed instruments (like the tanbur), and rebecs, due to the Prophet's (peace and blessings be upon him) saying: "There will be among my Ummah people who will permit illegal sexual intercourse, silk, alcoholic drinks, and musical instruments." The permissibility of the daff does not imply the permissibility of other musical instruments by analogy, because they have a stronger effect and stir souls more intensely.