In a spectroscopic binary, the two stars appear as one point of light, but the existance of two stars is revealed by their shifting spectral lines. This simulation shows how the orbit will determine what spectral shifts we see.Spectroscopic binaries will be in very close orbits, more often than not. A spectroscopic binary could also be an eclipsing binary if the two stars just happen to pass in front of each other. Otherwise, the Doppler Effect reveals their orbital motion. You, of course, know about the Doppler Effect. Also, this type of binary will show the spectra of two different stellar spectral types from a single point of light.