To split items based on transient on REAPER, you can use the built-in Dynamic Split window. It is quite advanced and bring pretty satisfying results in most case.
Though, you may find the need for more advanced stuff, especially in musical context, by pre-processing audio with having filters, or post-processing editing to put slices into REAPER sampler, aligning slices on the grid, or even convert to MIDI. Some could be with with extra individual scripts but having this in a self contained window allows to do fancy stuffs (like pre-processing part without render).
These features has been brought by cool as a REAPER free script, with a fancy waveform display GUI: MK Slicer.
Since its release, it has received a ton of updates, and even recently get updated to v3 yesterday, with even more features, mostly about flexible tempos.
You can see the full v3 changelog on the dedicated forum thread; as you can see, it is serious stuffs! There are other videos on the channel which trace the evolution of the script and give you more insight about how to use it.
It worth notice that cool’s MK Slider v2 has been forked by 80icio, in a version called MK Slicer 80icio mod. It brings all kind of stuffs to cool v2 version, and mostly at the time, multi tracks support for multi-mics drum editing and different transient detection algorithm. It could definitely worth to try this version as well, and it surely deserve a dedicated post cause the feature set have drift apart quite significantly.
Anyway, both version are free, so give it a try to explore all features and see how well it works, I only scratch the surface here!
Happy slipping! ✂
Feature Image Credits: cool