I know veeeeeery little about flstudio (on account of being lazy as hell), but if you get a mp3 or wav or something of the song, you could throw that in the audio clips, click on the name of the thing to bring up the channel settings, and under the Time Stretching field, change Resample to Auto (to keep the pitch from shifting) and crank the MUL dial to 200% or 300%
it'll play the clip at half or third speed if you do that, making it considerably easier to pick out notes; additionally, you could stick the pattern that you're building next to the clip to check against it note for note