Native speakers of English, please could you help me with my English?

I am reading a rather complex book about architecture (in particular about Frank Lloyd Wright) and find it difficult to understand some phrases. What does the word "singularly" mean in this context (the whose phrase i s"singularly expressed")

Wright's perennial ambivalence towards technique was never more singularly expressed than in this house (Falling Water Residence), for although concrete had made the design feasible he still regarded it as an illegitimate material - as a 'conglomera' that had 'little quality in itself'. His initial intent had been to coveer the concrete of Falling Water in gold leaf, a kitsch gesture from which he was dissuaded by the discretion of the client. He finally settled for finishing its surface in apricot paint.

Also, what does ''illegitimate" and "conglomera" mean"?