In 1947, interior is still valued as a “chief element.”
24. But the chief element of divine worship must be interior. For we must always live in Christ and give ourselves to Him completely, so that in Him, with Him and through Him the heavenly Father may be duly glorified.
The interior “completes” the exterior expression.
The sacred liturgy requires, however, that both of these elements be intimately linked with each another. This recommendation the liturgy itself is careful to repeat, as often as it prescribes an exterior act of worship. Thus we are urged, when there is question of fasting, for example, “to give interior effect to our outward observance.”[Roman Missal, Secret for Thursday after the Second Sunday of Lent]
Interior participation gives the “meaning and context” to the outward rubrics and texts. The premise suggests that the exterior worship is at the service of the interior, and that if there were a discerned way to deepen or make the interior more fruitful, the exterior aspects can and should be reformed to accommodate.
“Neat and well turned phrases” mentioned next recall MR3.
Otherwise religion clearly amounts to mere formalism, without meaning and without content. You recall, Venerable Brethren, how the divine Master expels from the sacred temple, as unworthily to worship there, people who pretend to honor God with nothing but neat and well turned phrases, like actors in a theater, and think themselves perfectly capable of working out their eternal salvation without plucking their inveterate vices from their hearts.[Cf. Mark 7:6 and Isaiah, 29:13] It is, therefore, the keen desire of the Church that all of the faithful kneel at the feet of the Redeemer to tell Him how much they venerate and love Him.
A suggestion that lauds exterior participation through singing, referring not to the Gospel accounts of Palm Sunday, but the traditional liturgical antiphon for that day:
She wants them present in crowds – like the children whose joyous cries accompanied His entry into Jerusalem – to sing their hymns and chant their song of praise and thanksgiving to Him who is King of Kings and Source of every blessing. She would have them move their lips in prayer, sometimes in petition, sometimes in joy and gratitude, and in this way experience His merciful aid and power like the apostles at the lakeside of Tiberias, or abandon themselves totally, like Peter on Mount Tabor, to mystic union with the eternal God in contemplation.
The site of the Transfiguration is an interesting reference. You might recall that Jesus didn’t endorse Peter’s plan to construct booths. In Luke’s Gospel, when the four (Jesus, Peter, James and John) descend from the mountain to find the crowds in need–exterior ministry beckoned.