Giorgio Moroder and Chicago - What's the link?

[The Boogie Doctor]

Hi party people,

I write to you all with a musical query. It has come to my attention that the tracks 'I Wanna Rock You,' written by Giorgio Moroder, and 'Streetplayer,' written by Chicago, both have the same descending melody/hook in their content. In the former track it is a synthesiser which features after the second chorus has concluded, whilst in the latter it is a hornline that constitutes the introductory passage of the song, famously sampled by Kenny Dope (Bucketheads) on his track 'The Bomb.' Furthermore, both pieces of music were released in 1979, which begs the question, however futile: out of Giorgio Moroder and Chicago, who originally wrote this particular melody/hook? Did Moroder, the grandmaster of Italian- and Euro-Disco pilfer musical content from mainstream American bands or was it the opposite, namely, did a mainstream US band purloin hooks from a relatively obscure Italian (then German) disco producer. I put these questions to you, the knowledgable people here at Discomusic.com.

Lots and lots of peace and love,
The Boogie Doctor.