We have measured single-particle inclusive spectra of ${\ensuremath{\pi}}^{+}$ and ${\ensuremath{\pi}}^{\ensuremath{-}}$ mesons produced at 2.5\ifmmode^\circ\else\textdegree\fi{} (lab) in the collision of 1.05-4.2-GeV protons, 1.05- and 2.10-GeV/nucleon deuterons and $\ensuremath{\alpha}$ particles, and 2.10-GeV/nucleon $^{12}\mathrm{C}$ nuclei with various targets at an angle of 2.5\ifmmode^\circ\else\textdegree\fi{} (lab). The negative-pion spectra show scaling behavior. The results are compared to a simple model in which individual nucleons in the projectile interact with the target to produce pions.