Fake instruments at Mass

Some days ago, in a post discussing liturgical candles, Fr. V. at Adam’s Ale said:

Here’s the rule: in the interest of symbolism and authenticity it must be a wax candlestick. Period. (I wish we could do the same for “fake instruments.” But that’s just me.)

When first I read this, my initial thought was that “fake instruments” are forbidden, but I couldn’t call to mind any specific document where this is so. Consequently, I set to work.

There is a liturgical principle that we only use in worship what is authentic and truly worthy of the Lord.

In the recent document Sing to the Lord, the United States’ Bishops Committee on Divine Worship stated:

Recorded music lacks the authenticity provided by a living liturgical assembly gathered for the Sacred Liturgy. While recorded music might be used advantageously outside the Liturgy as an aid in the teaching of new music, it should not, as a general norm, be used within the Liturgy (91).

Immediately following, the Committee gives a couple of exceptions to this norm: outdoor processions, Masses with children (when “used carefully”), and communal penance services.

Very often, such “fake instruments” are recorded and played while the accompanist plays the “electronic keyboard” as a separate instrument. This would is forbidden, at least in the Diocese of the United States of America (save those few exceptions).

Though I’ve not been able to locate it, it still seems to me that there is a similar – and perhaps stronger – prohibition on recorded music – and, I believe, “fake instruments” – in a magisterial document. Can one of our astute readers offer help here?