I'm familiar with what is said in the citation from Wikipedia posted above because of the music theory classes I have taken. Parallel fourths, fifths, and octaves are verboten in writing four-part harmony exercises, until you get into more advanced classes. The idea is "learn the rules first, so when you break them, you know why you are doing it."

I don't know what Josepp means by the term "parallelism."

I've studied classic guitar and play a batch of classical pieces, along with working out my own song accompaniments. Not often like Richard Dyer-Bennet's accompaniments, although I can if I want to. I use a lot of standard guitar chords along with right-hand folk techniques, and have no problem with strings of parallel fifths and such—unless I do it for a particular effect.

Josepp, can you explain more clearly what you mean?

Don Firth