Yep, did it with my DD too - by listening to her cries I could tell the difference between the grumbly grizzly but will probably go back to sleep in a few seconds cry and the "mum I need you" cry. Often it is a lot easier with the grumbles and grizzles to let them just gradually settle back to sleep as going in to them may well wake them up completely then you have a well rested (so they think) wakeful bub to try and convince that it really is sleep-time.

But definitely, if the tone of the cry changes to definite/demanding/distressed crying, go in and comfort them.