Great to see an Alec thread
That is a bit of a mystery; According to Hugh's discography and playing style, he recorded all albums except Fahrenheit. Alec did say to a fan in 1993 about a song that he wrote the bassline for it, and there are several SWW-era pictures of BJ with Alec in the studio and possibly one picture outside the studio in late 1991 / early 1992 with the band and Hugh playing basketball, though it's pretty unlikely that it's Alec on it since the body shape and eyes don't really match, his face isn't visible on the pic sadly. About the demos, we will probably never know for sure who recorded them, probably Hugh judging by the lack of the high pitched backing vocals. Lol
https://imgur.com/a/Acppnj5
https://imgur.com/a/xdZKM8i