Obviously the best way to hear whether your guitar is one that does need coating on your picks is to try both kinds of picks with your guitar. You can get an idea of the difference between the pick types on your guitar before buying any picks by using a flat plastic pick and a smooth copper coin such as a penny.
Lightly pick your low E string several times with the copper coin. This sounds very much like an uncoated thumb pick. Now lightly pick the low E string several times with the flat plastic pick. This sounds very much like the coated thumb pick, although the coated thumb pick will have a warmer sound.
If you are able to get a good sound from the copper coin on the low E string, you don't need coated picks. If the copper coin always sounds grating and annoying on the low E string, you should at least get a coated thumb pick, and for nylon string guitars, that's all you will need.
If you need coating, and have already purchased uncoated picks, see the Coating tip on the tips page.
To help you further, I've recorded a short sound sample on a Cordoba C10 CD/IN nylon string classical guitar, which is very resonant, to help you hear the difference between an uncoated thumb pick and a coated thumb pick across all the strings. I enjoy playing this guitar best with a coated thumb pick and uncoated finger picks.If your browser cannot play the mp3 files below, you may need to choose "Run This Plugin" if this prompt is visible above, or you can download the sound files to your computer to play them by right clicking the titles and choosing "Save...As..." from the popup menu.
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