The Southend High School for Boys Memorial Organ was given as a donation to the school from the Old Southendian Association in 1923. Built by Hill Norman and Beard for the sum of £1110, an organ for the school's hall was the chosen as a fitting memorial to those who gave their life fighting in the Great War. The organ was originally installed in what was a cloakroom off the hall of the school's previous site off Victoria Avenue. Now, memorial boards stand either side of the organ in its newer home on the Prittlewell Chase site.
Extensive damage was caused to the organ in the bombings to the school site of World War Two. Parts of the damaged organ were subsequently salvaged and stowed in the hall's balconies pending full restoration after the war.
When completed in 1953, the organ stood with actually more resources than before the war - it was decided that an extra rank of pedal pipes (an Open Diapason rank) should be added while the work was taking place.
Memorial boards now stand with the names of those who gave their lives in both World Wars, and the boards, organ, and remembrance books combine to form a complete memorial at the front of the main hall.
Not many changes have happened since the 1953 rebuild after the war and before the recent works on the organ, however their impact has been significant.
Firstly, in about 1975, the original Dulciana rank on the Great was replaced with a Fifteenth. The original Dulciana pipes that formed part of the casework remained in place, and came back in use about 33 years later as part of the recent expansion works to the organ. Then, in 1981, a two-rank Mixture was added to the Swell to add more "sparkle". Since then until about 2008 when the plans to expand the organ gradually came into action, no major changes have been seen in the range of ranks or sounds the organ can provide.
Between 2008 and 2014, the organ was expanded in a very successful school-based project, which saw 5 stops added to the organ. In 2017, OSOS was pleased to announce major professional work to the organ, which has involved its rebuilding, expansion, and incoropration of the work from 2008-2014.