TapeStop effect using stretch markers
This effect, also known as tape stop, or simply varyspeed, has been commonly used for spinning audio up or down, just like a dj would do it. Here is an appplied visual reaper example
Stretch markers are what you want if you don't have a plugin to do it. There are various granular plugins that will do it - uhbik-g is one if you use automation and most things by Glitch Machines wil allow it if you configure them correctly. However it can be done for free.
- Ensure that preserve pitch while changing rate is unchecked in the item properties of the item you want to spin down. Remember that, as you decrease the rate of the item, it will take up more space and may crash other audio further down the project in your time-line.
- Let's assume you want to do a spin down. Find the point in the item at which you would like it to begin and press control m to add a stretch marker. (command+M on Mac.)
- Press control shift enter. (command+shift+Enter on Mac.) This will expose marker properties.
- Ensure link start and end rate is unchecked.
- Your start rate should be 1.0, which is normal play rate. Your end rate should be 0.001, the slowest it will allow you to go. And there you have it. One spin down.
The difficulty is that it may not sound quite as you envision. The deceleration curve may not be quite right. In that case you will need to add more stretch markers to adjust the shape of your curve and things get quite messy because you need to make sure that the start and end rates all match up.
For example, let's say that you want the spin down to really get serious on the last word and it isn't really doing that yet.
Obviously you will need to insert another stretch marker at that point, the start of the last word, again with its start and end rates unlinked. It's start rate will read as whatever point on the descent you reached, much in the same way as putting another envelope point along an envelope curve in automation will give you the reading consistent with that point in the curve. You will have to change that start rate to a higher value though.
Let's say the start rate for our new marker is 0.094. You might want to try changing it to 0.199. Thing is, you must make sure that you change the rate of your previous stretch marker, the one we first added, to match that start rate otherwise the rate will jump.
Now let's say you want to do the whole thing in reverse, a spin up. One of the added difficulties here is that, for whatever stupid reason, Reaper won't allow you to put a stretch marker right at the start of an item. You will need to move a little bit in, meaning that the first part of your item will play at normal speed and then jump to the start rate of the stretch marker, which, for a spin-up, might be 0.001 assuming you want to start very slow.
You will also need to place a second marker at the point where you want the spin-up to end with its play rate set to 1.0 and its start and end rates linked this time. this is of course assuming that you don't want the spin-up to last the entire duration of the item.
You can get round this in a number of ways. Either create a fade so that the resultant pop caused by the little bit of unaffected item at the beginning is inaudible or, once you've placed the stretch marker, you could shrink the left edge of your item by the amount that you moved forward to place the stretch marker and then move the item back the commensurate amount on your project timeline.
You navigate between stretch markers by pressing control+apostrophe (command+apostrophe on Mac) to go forward and control+Semi-colon (command+semi-colon) to go back. Bear in mind though that this navigation also takes you to the item edges so if you navigate around and you're not able to bring up stretch marker properties by pressing control shift enter, you're probably not at a valid marker position.
many thanks to Justin M for this information