In the official recording, this riff is played with a device called a Talk Box. Since I don’t have access to a Talk Box at the time of this recording I cannot duplicate it exactly.
Here is a cool riff from Tull that has quite a bit of technique that all guitarists need to know. The ribbon-like symbol in the first and second measure is known as “vibrato.” This is when you rapidly shake the string being played with your fret hand. There are also a few slides, which are performed by sliding your fret hand on the strings while playing at the same time.