I think he's just talking about the sound quality recorded of vocals, not how to make himself sing better
Equipment can affect the outcome of the sampling of vocals in recording. My singing is quite dynamic, I use a lot of air on some parts, others just a slight breeze. My range is quite wide, even with mic technique, the mic itself may fault by not picking up frequencies in my voice that it needs to reproduce that 'killer tone' you speak of. I've had live performances where the way the in-house engineer mixed me, certain frequencies would simply disappear or 'cut-out' and people would tell me later they couldn't hear me singing at parts... this problem was solved when in with a cover act, we had a single engineer that took over at each performance, and he was familiar with my voice, and how to mix certain places where he knew I'd be close to the mic, but singing softer, and other parts when it was a full-out howl....
As is mentioned many times on this forum, the choice of equipment, the mics to be used for any particular singer is important. For me, live anyway, SHURE SM57 {edit} has been good to me. For bassier, softer, or crunchier parts, I go close to the mic, and for the high or soft parts I move away from it. Never seen it used in the studio - usually there is a more expensive mic in use...