The Holtkamp organ in the chapel of St. Thomas Aquinas originally began its life as the chapel instrument for the First Community Church of Dallas. The organ was acquired, along with the chapel and church property in 2006 as a part of the expansion of the St. Thomas Aquinas School. The Holtkamp organ was built in 1969, with Dr. Robert T. Anderson serving as the organ consultant.
Specification of the Holtkamp Pipe Organ:
| Great (I) | |
| Gedeckt | 8 |
| Principal | 4 |
| Flute | 2 |
| Mixture | IV |
| Dulzian | 8 |
| Swell to Great | |
| Swell to Great | 16 |
| Swell | |
| Copula | 8 |
| Rohrflote | 4 |
| Prinicpal | 2 |
| Quint | 1-1/3 |
| Pedal | |
| Subbass | 16 |
| Principal | 8 |
| Bass Flute | 8 |
| Choralbass | 4 |
| Dulzian | 16 |
| Great to Pedal | |
| Swell to Pedal |