The Otterbein organ was installed in 1897 and is probably the last organ Henry Niemann built. His oldest son, Frank, was most likely responsible for a large part of the instrument, because Henry died two years later in 1899. The original cost of the instrument, a memorial gift of Mr. and Mrs. Carl Greasley, longtime members of the church, by their family, was $1,500.00. Mr. Greasley died in 1894 before the extensive renovation in 1896. His widow presented the chandelier and the pews to the church at that time. After her death in April 1897, the family presented the organ in memory of both parents.
The Otterbein organ has 13 stops and 15 ranks. For each note in a rank there is one pipe. The cornet on the upper manual has three pipes for each note. In total, there are 842 speaking pipes made of pine, zinc, lead and brass.
The large pipes in the middle of the facade are speaking pipes. The pipes in the flats on each side are dummies. The case is all solid white oak, with the front of the case being all quarter-sawn oak. The organ is known among the Niemann organs for its bold, bright sound, excellent for hymn singing.
Restoration of the nearly 100-year Old Otterbein organ began in February 1990, when it was announced in a letter to Members and Friends of Old Otterbein that a campaign would begin to solicit funds to restore the organ in time for its 100th anniversary in 1997.
With gifts of $60,000.00 from friends and members, wedding fees and peanut sales to Orioles fans, the organ was restored by David M. Storey. The organ was removed from the church to Mr. Storey's Woodberry shop, a former textile mill, on January 11, 1994 and returned and rededicated on Sunday, December 11, 1994. Otterbein organist John Holland played Arthur Sullivan's "The Lost Chord".