Music is not allowed in Islam because it takes you away from remembering Allah (SWT). It is one of the tricks of Shaytaan to deviate us from the path of Islam. When music enters the heart, the Quraan leaves so that means, the music and the Quraan cannot co-exist in the same heart. When we listen to music, we waste our time, which could have been used to read, recite or memorise the Quraan. Music's beats promote movements of the body, in a way that eventually leads to dancing movements which is Haraam. Many lyrics of today's music are not permitted as Halaal within the teachings of the religion.
Allah says in the Quraan:
*And of the people is he who buys the amusement of speech to mislead [others] from the way of Allah without knowledge* and who takes it in ridicule. Those will have a humiliating punishment.
Surah Luqman 31:6
Al Hasan Al Basri said: "This Ayah was revealed concerning singing and musical instruments. (Tafseer Ibn Katheer 3/451)
The only exception is duff and nasheeds, which are Islamic songs without music.