Here is a translation of your text[1] and the critique that it unfortunately necessitates.[2]
So as to avoid confusion as much as possible, I specify that:
1) Your actual work in music interests me, not due to a transcendant quality that it would give you, but because of the most advanced developments at which you will certainly arrive by continuing it.
2) To the slight extent that such considerations matter to us, you yourself please me.
3) I absolutely refuse the general "theoretical" ideas of this text, which aren't linked to your work in music and which do not even come from you personally.
4) I obviously do not reproach you, in a general fashion, for submitting to influences or accepting the ideas of someone else. I reproach you for having accepted, in a clearly defined circumstance, several ideas that are stupid.
Cordially,[1] For a concept of musical experimentation, presented September 1957 and approved by the Italian section [of the Situationist International], except for Gallizio and his son, Giors Melanotte.
[2] Developed by Guy Debord in Remarks on the concept of experimental art, an internal document dated 15 October 1957 and printed in an edition of 17 copies.
(Published in Guy Debord, Correspondance, Volume 1, 1957-1960. Footnotes by Alice Debord. Translated from the French by NOT BORED! October 2005.)