ffplay - Is there a way to display a video and spectrogram in the same output?
Use

ffplay -f lavfi 'amovie=/Users/hdl/Desktop/HDLS3K.mp4:s=dv+da[v][a];[a]asplit[asp][out1];
   [asp]showspectrum=size=1280x512:mode=separate:slide=scroll[spect];
   [v]scale=640:-1[v];[v][spect]vstack[out0]'


amovie usually selects only one (audio) stream. dv+da gets it to extract the best video and the best audio stream. The video output is scaled so that the vstack works.