help me please! vocal and guitar match problem

hello. I'm new in recording and trying to learn reaper. After I have recorded guitar part, I'm recording vocals in second channel while listening guitar with headphones. problem is, despite recording in the same time, my vocal record on channel 2 appears late after recording is over and doesn't match with guitar. Because of this I'm trying to find the right spot and move the vocal part where they start together. why they don't match after recording is over even there is no problem when recording? is there something that I'm missing? thank you for now.

Hello and welcome emreabay! You are missing one of the very important first setup tasks with a new DAW. "Aligning" playback with recording. Background: The computer has some lag from input to output. You set this. (It's called block size.) A very fast high spec computer may let you set that small enough to run live sound with no perceivable lag. However, what is most common is to monitor any live inputs through the mixer built into your audio interface (which has a mini DAW-like mixer built into it just for that use). This lets you use a slower computer and/or save processing power for the mix instead of using up resources for live near-zero latency sound. If you have an external audio interface, this is the easy SOP option. What to do with that info: So if you're doing that 2nd thing - monitoring through the interface - you need to tell Reaper what that lag is so your overdubs are precisely nudged back to alignment with your original tracks. How to do it: The setting is in Preferences/Audio/Recording You can let the driver guess or manually enter your own offset or use a combination of driver reported lag + your additional offset. Plug an audio cable from an output to an input and record some sample from track 1 into track 2. Use a sample with an easy to see peak you can zoom into. You'll see the recording in track 2 ahead of track 1 (just like your overdub was). Enter the offset value needed to align them.

You should just be able to flip the "direct monitor" switch on the Scarlett and not have to fiddle with manual latency compensation.

Try changing the PDC preserve setting for either track and see if that helps. (Right click on the record arm button for the track, you'll see it as an option). It's a bit confusing, but depending on whether you are monitoring via Reaper with plugins on that track it creates a lag on the signal you hear when recording that part, however, as humans, we can auto-compensate for any latency when playing/singing. However, the problem comes that Reaper either tries to offset that part to match or (Depending on setting) keeps it as recorded, so if you've sub-conciously auto compensated yourself, this needs to be reversed, or it ends up putting you out of sync trying to help. I have to change that PDC setting for many of my guitar tracks to get them to come good, but really it depends on what you're focused on when playing as to which setting works best for you (i.e. are you sub-conciously listening to the music you're playing to, or the instrument that you're playing). The higher the buffer/latency with your setup the more of an issue this is.... Thankfully the PDC Preserve works a treat, and wish it was on more DAW's. I've not dived in on the entire mechanism behind it, but generally i preserve PDC on any track that i monitor via Reaper (i.e. using amp sims etc.) ... Any clean 'direct' monitoring is left as is (i.e. if recording direct from my guitar amp).

Even if you are monitoring through REAPER, with only two tracks on the go it shouldn't be a problem to drop the buffer to a near-noticeable amount of latency ("Request Block Size" in REAPER prefs under Audio > Device, or change it via the Focusrite driver, whichever is recommended for Windows machines).

In my experience the Focusrite hardware does a fine job of reporting it's latency correctly to Reaper. Of course mileage may vary, but i would definitely try the PDC Preserve option as stated above before messing around with Audio Interface settings etc. Which can have an adverse effect if you don't know what you're doing/changing. Discussion on the matter here:-