If C is a g-nodal canonical curve with normalization ν: P1 →Pg-1 then a line bundle L of degree k on C is given by ν*(OP1(k))≅L and gluing data (bj)/(aj):OP1⊗kk(Pj)→OP1⊗kk(Qj). Given 2g points Pi, Qi and the multipliers (ai,bi) we can compute a basis of sections of L as a kernel of the matrix A=(A)ij with Aij=biBj(Pi)-aiBj(Qi) where Bj:P1→kk, (p0:p1)→p0k-jp1j.