I'd worked on the structure of 'Whole Lotta Love' on my own at home and I couldn't wait to bring the band together to get this whole thing going. I knew deep inside that this was a riff that everyone was going to enjoy playing. It was so infectious.

'Whole Lotta Love' and 'What Is and What Should Never Be' were two really strong foundations to start off the second album. Unlike with the first album, having to dip in and out of Olympic whenever we could at ten or eleven o'clock at night for an hour or two, we could actually book sessions consecutively this time because Led Zeppelin were seriously on the map now.

We went to Mystic, which was the old Del-Fi Studios… and we did 'Lemon Song'. We did a couple of tracks in there and that was really cool.

During the Yardbirds, I played on my Vox Phantom XII… It's also on 'Thank You' so it's had quite an interesting life.

We did 'Heartbreaker' in A&R and then I did the guitar break in the other studio with a totally different sound. I thought, let's over-pump the difference of sound for the middle solo guitar and it'll just be like someone who's been in the studio, opened a door, and then this thing goes like that, and shut the door again and we're moving on in rhythm.

Generally, I would put the solo on last if I could, once all the vocals were done. There is a whole section of recording in New York at A&R and Groove Studio with engineer Eddie Kramer, doing 'Ramble On' and 'Heartbreaker'.

We went to Mystic, which was the old Del-Fi Studios. The room was really live with reflective surfaces. We did 'Moby Dick' because it was great for drums.

Every studio had a different room and had a different sound perspective and ambience to it. It was all an exciting discovery. Clearly, for me, it was hands on for all of this and a bit later we even put on the vocal overdub for 'Bring It On Home' in Canada in some little hut.