Involved in the early to middle stages of 60S ribosomal subunit biogenesis. Core component of box C/D small nucleolar ribonucleoprotein (snoRNP) particles. Required for the biogenesis of box C/D snoRNAs such U3, U8 and U14 snoRNAs (By similarity). Part of a large pre-ribosomal ribonucleoprotein (RNP) complex, that consists of at least 62 ribosomal proteins, 45 nonribosomal proteins and both pre-rRNA and mature rRNA species. Within this complex directly interacts with TCOF1 in an RNA-independent manner. Core component of box C/D small nucleolar ribonucleoprotein (snoRNP) particles; the core proteins SNU13, NOP56, NOP58 and FBL assemble stepwise onto the snoRNA. Interacts NOP1 and NOP58. Interacts with NUFIP1, RUVBL1 and RUVBL2; RUVBL1:RUVBL2 seem to bridge the association of NOP56 with NUFIP1 (By similarity). Widely expressed, with highest levels in the central nervous system (CNS), including cerebral cortex and cerebellum, and spleen. In the CNS, expressed in Purkinje cells of the cerebellum, as well as in motor neurons of the hypoglossal nucleus and in the spinal cord anterior horn (at protein level). Belongs to the NOP5/NOP56 family.