Are five octaves enough?

A worldwide study was done on the ranges of 150 celesta songs, in which it was found that a four-octave range was enough to play 80% of the songs. Actually, when Mustel invented the celesta in 1886, it already possessed a four-octave range. Even today, the majority of songs are found in this range.
A five-octave range is required to play Holst's "The Planets," Respighi's "I pini di Roma," and Stravinsky's "Petrouchka" (all composed in the 20th century). A five-octave range is sufficient to play nearly any song in existence.
However, there are two famous classical pieces that need an even lower range. They are Gustav Mahler's "Symphonie 6" and Leonard Bernstein's "Symphony No. 2." Yamaha has developed celestas with a range of up to five and a half octaves, in order to play such modern pieces. A half octave consists of five notes . These celestas are equipped with large resonator boxes in order to reproduce these five low notes, and have complicated action mechanisms.