We prove an explicit formula for a projection of singular vectors in the Verma
module over a rank 2 Kac-Moody Lie algebra onto the universal enveloping algebra of the
Heisenberg Lie algebra and of $sl_{2}$ (Theorem 3). The formula is derived from a more
general but less explicit formula due to Feigin, Fuchs and Malikov [Funct. Anal. Appl. 20
(1986), no. 2, 103-113]. In the simpler case of $A_{1}^{1}$ the formula was obtained in
[Fuchs D., Funct. Anal. Appl. 23 (1989), no. 2, 154-156].