D.K.N. has kindly shared with us this remarkable newspaper article from 9 April 1964:
Vatican City (9 April 1964): Pope Paul VI has sought to assuage the fears of those who see the ecumenical council’s Constitution on the Liturgy (Sacrosanctum Concilium) as possibly spelling a new eclipse for Gregorian chant. Speaking to a pilgrimage of French teachers of plain-chant, the Pope said: “Are any of you perhaps alarmed at the future applications of the Constitution on the Sacred Liturgy which was adopted by the council fathers and promulgated by us last December 4th? Let them read that admirable text’s passage concerning liturgical chant, and particularly the following: The treasure of sacred music is to be preserved and fostered with great care…” (Sacrosanctum Concilium, Paragraph 114). […] The Pope declared: “As our predecessors often pointed out, this chant has all the qualities required in religious music.”
A picture of the pope circa 1964: