Explanation:
1. Some Muslims believe that only vocal music is permissible (halal) and that instruments are forbidden (haram). Hence there is a strong tradition of a cappella devotional singing. Yet some Muslims believe that any instrument is lawful as long as it is used for the permissible kinds of music.
2. Nasheeds are moral, religious songs sung in various melodies by some Muslims of today without any musical instruments. However, some nasheed groups use percussion instruments, such as the daff. Singing moral songs of this type without instrumentation is considered permissible (halal) by many Muslims.
