Just noting for once that I answered my own question before even posting this time
SC defines Formlet (a resonator) as
Ringz.ar(in, freq, decayTime) - Ringz.ar(in, freq, attackTime)... after some poking about, I found ELSE library's [resonant~] which, just like SC's Ringz, is a constant skirt gain bandpass filter and takes the same inputs (frequency, and 60 dB decay time). So it's a direct translation...
Will formalize it as an abstraction with args later.