these days, most recording sessions for rock or pop groups are recorded directly onto computer hard disk, using a program called ProTools by these rich mad scientist cum marketing types from a company called digidesign. Think of it as a giant iPod, or more like 192 iPods all strapped together with software, so that you can have the bass guitar on one, the bass drum on another iPod, the snare drum on another iPod, the lead singer's vocal performance on yet another 3 iPods (he sang it 3 times, with slight variations on the lyrics, and he  can't decide which one he  likes the best, so he made the producer (like a film director for a record,) save them all separately, for later Decision Postponement options. )
 Anyway, one killing feature of this newish recording technology, (which has been around, in stereo form (not the 192 channel upgrade...) since the late 80's. . . ) is that you can actually go in and cut and paste one tiny smidgeon of a note from one performance into  another, and the listeners (if there are any!) can't tell. So say the drummer hit one snare beat a little late, cuz he was scratchin his nose, or something (!). . . or a little weaker than the others. The engineer and producer, if so inclined (control freak, mechanical performance nazi or just fastidious and/or  anal....) can copy a different snare hit from another part of the song (or even a WHOLE CHORUS of the drums, if that chorus is played 'superior' (by who's def?) to the one being replaced....) anyway they can copy the good note, and paste it over the old note, thus P E R F E C T I N G the performance.
Well, what this leads to, some say is unlimited freedom. Others say it takes the soul-life out of music today. . . In my opinion, it's a little of both, but it can be fun and help get the job done, and sometimes, with creativity be an improvement, In my case, I get to do maybe 6 performances of the same tune, cuz there's a lot of hard disk space available to record my ideas on, and that it's an invitation to experiment (for me the musician,) with a safety net, that if they don't like my improv, they still have the earlier 'responsible' performance i gave while the clock was running. = but that's multiple complete takes, not cutting up takes and putting them together, which is what KH won't do. so i've strayed - sorry.
  Well, dare I say, Kevin Hupp is a really good drummer, and cool guy. When he gets your music-minus a drummer recording in ProTools format ( FedEx him the hard drive, or there's even a new way to collaborate over the internet....) (big bux for Digidesign yet again!) well, when Kev gets your song, he'll set up his studio to play it back in his headphones, where he's sitting at his humongous drum kit, and he'll play along, recording his drums on a number of additional ProTools tracks (a bunch more of iPods, using the early analogy on this page....) And  there, you'll have it - a groovy drummer recording a groovy drum track on your music. He then FedEx's the hard disk with your song, now including his contibuted drum performance, back to you, you pay him (not sure which order this occurs in!) and bob'syeruncle. Plus you still haven't mixed it yet - you can decide how loud you want drums in the mix when you get it home.
  But the cool part is this: Kevin won't do that cut and paste thing with his drum tracks recorded at his studio. You are guaranteed that what he sends you will be a complete performance of his, from beginning to end. (He will do more than one i think, but whatever he records and sends you back, will be a complete 'take' from beginning to end - no spliced in bits.) He contends (and many will agree, mostly mystical types like myself....) that there's a certain magnetic continuity to a musical performance, it's an event, in real time captured forever, and when people start cutting and pasting to make it a more 'perfect' performance, this ineffable 'vibe' is lost. You mightn't hear the difference, but you feel it, maybe consciously, or maybe just as a vague sense that something is missing or undirected.
 End of speech.