I'd personally recommend no solo organ during low Mass during lent and advent. Don't forget: you can still use a capella hymns and choral music.

"No music" is not a Catholic liturgical ideal in any meaningful sense.

Then: be careful what you ask for.

Bad idea to propose "no music whatsoever" to the pastor? I'm not exactly sure what you're getting at with your last comment.

'Twould be fine by me :) In fact, that's the plan for the Christmas Day Low Mass this year anyway.

The 1960 Rubrics for the Missal refer to the document De Musica Sacra (1958), of which tranlsations may be had here and here, and although this is done specifically to note that it covers congregational participation, it goes to show that this document is most likely rather current, '62-wise.

In De Musica Sacra, no. 80 marks the beginning of the section where the times when the use of organ is prohibited are discussed.

For these times, it specifies the non-use of organ for all liturgical actions, "omnibus actionibus liturgicis" (excepting of course Benediction of the Blessed Sacrament). Further exceptions are then made for certain days, which part seems commonly understood. However, a final exception is also made that "the organ only may be used at Mass, and Vespers for the sole purpose of supporting the singing" (Adoremus' translation), which I find to be interesting.

For one thing, the way it seems to me, this exception for use "in Missa et in Vesperis, solummodo ad cantum sustentandum" seems to regard the fact that Mass and Vespers are the primary liturgical items which a parish might sing.

Consider the Liber Usualis, which is at its most thorough with respect to Mass and Vespers, and for this reason.

The Liber, when it provides Lauds, does not point the psalms for Lauds: because, if you are ambitious enough to be doing Lauds, why would you need the pointing? In a similar fashion, this instruction does not foresee that you would need un-seasonable organ accompaniment to support the singing of Lauds: it limits this exception to Mass and Vespers.

Then for different thing, consider how everyone admits the singing of English hymns before and after a High Mass, on grounds that they are not part of the Mass. Because of their not being deemed a part of the Mass, I would argue that by this consideration they are rendered ineligible for this "for the sole purpose of supporting the singing" exception, due to the wording "in Missa".

Thus, it seems that this exception was intended more along the lines of encouraging singing-the-Mass, and singing Vespers, than otherwise.

Anyhow, I would consider it perhaps arguable that you could use the organ to support singing during a Low Mass (though whether this was intended, I don't know); but as far as I have thought about it, I would say that the documents seem to prohibit the use of solo organ during the same; and I would also argue that organ ought not to be used outside of Mass and Vespers at all, even though it should be necessary to support singing of some random hymn-or-other, as these would be sung during the processional / recessional, and these would seem to be liturgical actions, as far as I know.

So, that's my thinking on this, at present.

Anyone interested in Catholic liturgical ideals comes to our High Mass later in the morning. The Low Mass crowd is mostly indifferent to music, as evidenced by their lackluster hymn singing.

If they're indifferent, why not make it a high Mass?

When I'm not able to get to the nearby (35-mins) Sunday Latin Mass at another parish to sing, they simply have a Low Mass.
There is a young "Anglican" man who plays the organ.
Unfortunately, it seems that he may not be interested in my "reminders" to not play during the Mass during Advent and Lent. Sometimes, though, he remembers and lays off the meditative playing during Communion.
We never have congregational hymns during this Mass, just the processional and recessional.

Steve, it's not an ethnic German parish (unfortunately?), but we usually do a three-hymn sandwich with no singing during Communion. Do you remember what the custom was as far as playing the organ during those weekday Masses in Lent? The prohibition on organ playing seems to be widely ignored in Germany and Austria except during the Triduum. When I attended SSPX Masses (High) in Germany during Lent, the organ was used just like at any other time of the year, including interludes and other solo playing during the liturgy. They also substituted German hymns for the sung Proper. An FSSP Mass I went to was the full "German High Mass" - German hymns replaced the Proper, Ordinary, and even the Asperges. Of course, there's no custom to justify such thing in English-speaking countries, and doing so would rightly be considered an abuse.

at/during EF Low Mass, I think it is unfortunate that hymns would not be employed

At a Low Mass, there often isn't already-built-in time for hymns. And if the congregation at one is small enough, there isn't much of a point to a Communion hymn, either. You have your time for personal Communion prayers, and then Mass is already continuing on. Unless we just want to ask the priest to sit and chill for a bit so that hymns could be added, meditative organ is usually best at a Low Mass, and it doesn't last all that long, either.

My practice, when I'm asked to play at a Low Mass with Organ is this: choose an appropriate Ordinary; play Introit, and Kyrie before celebrant reaches the end of the prayers at the foot of the altar, then pick up again after the Credo (or Dominus Vobiscum) with the Offertory Antiphon, Sanctus & Benedictus from chosen Ordinary; post Consecration I borrow from various chants (including the Requiem and Victimae Paschali Laudes and Lauda Sion,... among others). During the distribution of Holy Communion I use the Agnus Dei (from the Chosen Ordinary), the Communion Antiphon, and (as necessary) either a chant hymn or something similar, improvised. At the end of Mass, I intone Salve Regina and then accompany the congregation who usually sing lustily. After this, as Father retreats to the Sacristy, I improvise a postlude.

We will continue High Masses throughout Advent and year-round. The Low Mass with music is offered earlier in the morning. The pastor is fine with no music at that Mass during Advent except on Gaudete Sunday; therefore, I will look forward to sleeping an hour later for three weeks, without any reduction in pay!