I’m not sure if he’s using an lfo to get the modulated sound or just notes with long release??
Its a fat arse baseline and i love it!
You need to use a basic synthersizer like sylenth1. Set osc 1 to saw wave, -1 octave and 1 voice. Set osc 2 to pulse wave, -1 octave and 1 voice. Set the attack to ca. 0,90. Add a chorus effect. Tweak with the chorus settings to get the sound you linke and adjust the dry/wet to about 40 %. To get the modulated sound, add a sidechain compressor on the synth channel and sett the “audio from” to your kick drum. You can also use a lfo within a synth like Massive, or you can automate a lfo. At last add some reverb. I uploaded a picture to my website to make it easier for you. The password to access it is “bassline”.
Here is the image: http://www.jvsfstudios.com/client-downloads.html
That should do it! I hope it helped