Of the various types of bell that have been used in the orchestra over the centuries the tubular bells, arranged chromatically as symphonic chimes, have become part of standard instrumentation in the modern opera and symphony orchestra. Their main role was to act as a substitute for bells in the orchestra, but nowadays their timbre is valued in its own right. Tubular bells were developed as an easily portable instrument for everyday use in the orchestra. Their sound was intended to be as close as possible to church bells, a target that they never reached, however. They are used in the higher register, while the lower register is covered by the bell plates, although the sound characteristics of the two instruments are very different. In the past, solid steel bars were also used as bell substitutes.