The quotes below make it clear why Porter deserved a songwriting co-credit for The Smiths songs he worked on - or, as I've always argued, why the credit should have been 'Music by Marr, Porter, Rourke', 'Song (i.e. vocal melodies and lyrics) by Morrissey'.
"They didn’t really know about recording. They didn’t know about overdubbing or about song structure or anything, Johnny would just play a riff which would go on for two and a half minutes, Morrissey would sing over it, and that was it. I tried to bring in some light and shade, because they didn't necessarily have verses and choruses as such in their songs, so I used to try and arrange the dynamics of the song. That's why we came across a sort of formula of having a guitar intro, a breakdown in the middle and a ‘re-intro’."
"We'd make the guitar lines play in a lower register below the vocal during the 'verse' and then break out into a higher register during the 'choruses', adding harmonics, backwards echo and doubled melodic hooks etc (all on the guitar)"
"There were certain parts of the song I would try and build up more, so that there was more of a sense of tension and some release from it to make it more of a pleasant journey, rather than such a linear thing"
"The band didn’t really do demos, but usually they’d have a basic idea or a structure of whatever song they wanted to do, but with How Soon is Now? there were no pre-conceptions. I never heard a demo. [Johnny Marr recalls demo’ing the track, then dubbed ‘Swamp’ before the recording session, before building up the song into the tremolo-daubed monster it became with John, Ed]"
“I programmed the LinnDrum (again!) congas, shakers and cowbell and tambourine. to get a groove thing going in the room. Those elements remained in the final mix.
“Johnny will probably dispute this but I remember sitting in the studio playing That’s All Right Mama on the guitar, saying to him ‘let’s do something like this, just stay on the one chord (F#) for a bit. ’I remember asking Johnny if he had any other licks, and he had this thing that was in a high register. It actually sounded a bit like William, but I asked him to play it two octaves down and slow it right down. That would become the B-section. So, they all started playing, along with the box and what you hear is , after an amount of tinkering, the eventual result.”
“A lot of the dynamic arrangement and sequencing was assembled in the mix, The band didn’t play it quite as it sounds. For the re-intro, I just switched out the drums and the bass and let the guitar play on its own.”