The invention is a process for hydroformylating multicomponent syngas feed streams containing CO, H.sub.2, C.sub.2 to C.sub.5 olefins and mixtures thereof and C.sub.2 to C.sub.5 alkynes and mixtures thereof by contacting the multicomponent syngas feed stream with a solution of an oil soluble rhodium complex catalyst produced by complexing in solution a low valence Rh and an oil soluble triorganophoshorous compound wherein the catalyst has a P/Rh ratio of at least 30, a concentration of Rh in solution from about 1 to about 1000 ppm by weight, a total concentration of coordinatively active P of at least about 0.01 mol/l, and a ratio of [P]/p.sub.co of at least 0.1 mmol/l/kPa, wherein [P] is the total concentration of coordinatively active phosphorous in the solution, and p.sub.co is the partial pressure of CO, to produce the corresponding C.sub.3 to C.sub.6 aldehydes. The process has utility for the hydroformylation of streams that contain olefins and alkynes.