Jonathan Petersen (1881-1961) was an organist and composer living in Greenland. Most famously, he wrote the music for the Greenland national anthem; the lyrics had been written by Lutheran pastor Henrik Lund.
Nuuk is the capital of Greenland and there are two primary churches there, the cathedral and the Hans Egede Church. This article gives some basic information about the recent evolution of the Lutheran church in Greenland. Peterson conceivably could have been organist at either or both of them, though there is a bronze bust of him in front of the cathedral leading me to suspect his primary work was there.
The stamp includes a set of facade pipes in addition to Petersen's portrait. The pipes are not identified. They could however be representations taken from the facade from the in organ currently in either the cathedral or the Egede church. Both instruments are relatively new (1970 and 1971), so Peterson never played either of them. Absent any other information, one might conclude based on circumstantial evidence that the pipes on the stamp are part of the facade from the current cathedral organ.
Randall Harlow has assembled a very helpful website describing the pipe organs of Greenland. The page for Nuuk includes details about both the cathedral organ and the Hans Egede Church organ. Neither facade is exactly like the one in the stamp image however.
The stamp was issued September 5, 1991 as part of a set of three portraying famous men of Greenland.
.Marcussen organ in the Nuuk Cathedral (2 manuals, pedal, 11 ranks)
(Copyright 2010 Randall Harlow.)
Nuuk Cathedral exterior