|Fritz on the cover of BCN magazine|
Back in the late 70s, as I learned the story, he wanted to do some research and include sexual orientation as one of the variables measured. Yet when he went to look for suitable metrics, the only one on offer was that compiled by Alfred Kinsey back in the late 1940s: the "Kinsey Scale" that grades sexual orientation from 0 to 6 according to whether your attractions are more to members of your own gender or another.
Kinsey's line is pretty easy to understand - add up your partners and divide by the number you first thought of. However this is painfully limiting: for example, by scoring the number of people with whom someone has had sex, you might get quite the wrong idea about someone who found their way into a particular kind of sex work, or who dare not act on their true attractions due to family or legal pressures.
Klein set about devising his own set of measurements, leading in 1978 to the "Klein Grid", a 21-dimensional measure looking at different aspects of life and the past, present and ideal states. It's less a number, more a couple of phone numbers complete with trunk dialling codes, but it does a far better job of accommodating issues such as sexual orientation changing over time, coming out in later life, or being better at pulling with one gender than another. It's still not perfect: like the Kinsey line it's binary in its model of gender and relies on the idea that gender is in some way a factor, and cannot account for things like preferences for a younger or older partner, fetishes, or whether attraction is romantically or sexually driven. But like Kinsey, even where it fails it gives us a language to articulate around sexuality and attractions that we did not have before. For bisexual people especially this was a greatly empowering new lexicon.
My main personal memory of him is from BiCon 2002, arguing with me whether the bi movement should still strive for printed publications; he saying no, me saying yes. Broadly his position was that everyone had private internet access so there is no need for the cost and grunt-work of print, while mine was that physical objects have permanence and tangibility. I think our different socioeconomic and geographic backgrounds meant we were coming at the question from two very different perspectives, but it was a happy and friendly argument.
Arguing their case and open to hearing the opposing view: it's a good way to remember someone.