When you get recorded, do most professionals record one riff and duplicate it as many times as you need to in the song, or do you just play the whole song through.

For example, one of my verse riffs plays 4 times. Will they just record the verse riff once and duplicate it 4 times, or will i play the same thing 4 times?
Usually they record the whole section, and they usually record each repeat, instead of just copying it. It helps keep things from sounding to mechanical, if you ask me. They may record each section seperately instead of the song all the way through, though, especially with vocals (Ozzy was well known to always double his vocals, and do it one line at a time).
It's about what the producer and artist want to do. When looking for a studio when I was in my former band I contacted one guy and asked him what he normally does. He told me to have the band practice the songs as much as possible because he liked to record the entire band at one time to save time & money and he would spend more of the time mixing and mastering. This caused me not to hire him.. one being I am a big fan of overdubbing and adding more instrument parts that are impossible to play live.

When I bring in session people for my songwriting demos, I give them a chart and ask them to play the entire thing. This becomes the scratch track. I then have them record, let's say, the intro and verse.. then stop.. listen to it.. if it's good.. time for the pre-chorus... okay sounds good.. now the chorus. If I'm relaly picky I'll pick the best time they played the chorus and just repeat it. This is more common when I'm using instruments since I like the vocals to be SLIGHTLY different each time lyrics are sung.

After the basic tracks are done, I usually ask them if they want to do any overdubs if I don't have any written. Again, these are for demos.
I was once heavily prominent on these forums from 2004-2007, let's see how long I can stay now that I'm back.
usually they dont, it requires less editing, and it wont sound so repeatitive. Even if you play the same riff 4 times, each time you play it, it will have a slight sonic difference. Plus its being lazy, you, yourself as a player, shoudl want to take more pride in their playing and would take the time to play your songs properly.

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I dont like when people record and loop the music at ALL

it sounds really fake. in a BAD way

However i do like that Ozzy thing and i do it too. I record each line in the vocals seperately, and make each part as PERFECT as i can. And when i finish, i have an AMAZING take! No weak points at all.

You can also do that for guitar. ie: recorded verses, record choruses, then record solos
Well I think the best method would be do it in chunks. Not duplicate everything, but take the time to work on each section to sound good. I definitely don't want it to sound fake/mechanical.

Thanks guys!
I've tried a lot of different methods.

I find that some work better than others.

For vocals I've tried line by line, take by take, and multiple take cut and paste. I've found that line by line seems to work best as long as you plan it out properly, or else things can start sounding very unnatural, you really have to justify where your lines start and end. And copying the vocal parts for choruses.

For guitars I've done, section by section, however I've found that nothing beats the sound of a doubled solid take of the entire song, especially if it's doubled.