How to get the reverse guitar sound
This type of sound is mainly associated with two very specific songs.
I'll describe what this sound is, where most people heard it first, how this sound used to be made, then how it's made now using modern digital recording.
What this is: A single track of audio played backwards.
Where most people heard it first: Strawberry Fields Forever by The Beatles (released February 1967) and Castles Made of Sand by Jimi Hendrix (released December 1967). In guitar circles, the Hendrix song is given more attention.
How this sound used to be made
This is where things get interesting.
In the old days of multitrack audio recording, reel-to-reel tape systems were used, and recording backwards required flipping the reels around. In later years when the technology got smaller, this could be done with compact cassette recorders like the Tascam 424, and that's how I used to do it.
My process on the 424, a 4-track machine, was to always put my reversed audio on track 4 just to keep things simpler. I would record stuff to tracks 1, 2 and 3 first. Then I find the section where I went the reversed audio to be recorded, go to the end of that section, stop, flip the tape over so track 4 is now track 1, record my stuff, stop, flip the tape back over, adjust levels, done.
I make it sound easy, but it really wasn't.
How this sound is made now
Software can reverse the playback of audio very easily, but that doesn't mean the process is simple because there is still the multitrack environment to take into consideration.
You'll notice in the video above that, thankfully, when you do a select-all of a track in Audacity and reverse it, the software "mirrors" where both the audio is reversed and placement of the audio itself is flipped, almost like reversing a photo in an image editor.
I can't adequately describe in words how nice this is. When both the audio and the placement of audio is reversed, there is no need to worry about timestamps. You reverse, record, reverse again to bring it back to normal, and all the timestamps line up. This is simply lovely.
How to reverse guitar in Audacity
See the video above as a reference as I'm describing what I did there here.
Step 1. Generate a rhythm track on track 1.
Step 2. Record your primary rhythm guitar to track 2.
Step 3. Count the number of peaks in the rhythm track from left-to-right and remember this number. You'll need it in a moment.
Step 4. Select-all track 2.
Step 5. Effect > Reverse
Step 6. That number you remembered from step 3? Now you need it. Count the number of peaks from right-to-left so you know when to stop recording. That is your end point.
Step 7. Pick a spot before that end point and record a second guitar (this is the one which will be reversed) to track 3.
Step 8. Select-all tracks 2 and 3.
Step 9. Effect > Reverse. This reverses track 2 to normal and track 3 to reverse.