I consider this a serious matter meriting serious discussion, not flippant dismissal

Well you are going to get the flippant dismissal. LOL. You will just have to burn your mantilla and syllabus of errors in protest - speaking of protestants with a little "p." I am Byzantine, but love the organ. You understand there are no instruments in Byzantine churches, so I have already crossed a quite minimal line to work for Latins. Is outrage!!!

I suspect someone could make an argument for praying with and playing for other baptized Christians even if they are not Catholic. I don't make that argument, but find Latins generally less objectionable than Protestants, for those who concern themselves with such things.

If not, they should ask themselves whether the sacrilegious and invalid administration of sacraments might not be objectively more offensive to the Holy Trinity than prayers to a false deity.

Other than baptism and perhaps marriage, what other sacraments do Protestants have? None. Some would say they do not even have valid churches. Since no real sacramental worship takes place to begin with, I see nothing any different than playing for a ball game or a school function. However, I will say that the Protestants I have worked with often represented a higher level of Christian behavior and charity than many of the Catholics.

Many Protestants, and I mention Baptists in particular, don't understand the concept of sacraments. Baptism is an outward sign of an inward grace, as they say. Communion is a meal in remembrance of the original Lord's Supper. There are no validly ordained sacramental clergy. It isn't a pretend sacrament. It was never presented as sacramental to being with.

I once worked in a Christian Church (Disciples of Christ) in which communion was a sign of unity. No sacrament was ever implied. An interesting aside, members would sometimes be re-baptized because it made them feel better. They considered it as something of a re-commitment ceremony.

I think the danger in Catholic/Protestant discussions is that we often use the same terms, but mean entirely different things.

Catholics have no business participating in these rituals, even if that participation is limited to providing background music.

This Catholic doesn't take direction from those with no authority to give it, no matter how well-meaning they are.

As I mentioned in an earlier post somewhere, I haven't played for a Protestant church in over 15 years. My understanding, though, is that the Church does allow it and no longer forbids it.

I've never had the impression that Protestants think of their "communion" as a Sacrament. I'm not sure they even believe in Sacraments the way Catholics do, even though they use the word "sacrament" in reference to their baptism, communion, and confirmation. Sometimes I wonder what, exactly, they think that baptism is for. Just because they use enough of the correct words with some water doesn't mean they are intending to do the same.
I had an argument conversation with my husband's great-grandmothers (Methodist and Church of Christ) about my first son being baptized "so soon" after birth.
The one from the Church of Christ had the "how could a baby have any sins to be repentant of?" thought (which is what they believe it is - a sign of repentance, not having anything to do with Original Sin). The Methodist (who hated Catholicism) said "well, Catholics believe..." (which was probably the only time she used that phrase correctly). While Methodists use the term "sacrament of baptism," they also aren't doing it to remove the stain of Original Sin.
From the UMC

baptism, as a means of grace, signifies God’s initiative in the process of salvation. John Wesley preached “prevenient grace,” the grace that works in our lives before we are aware of it, bringing us to faith. The baptism of children and their inclusion in the church before they can respond with their own confirmation of faith is a vivid and compelling witness to prevenient grace.

Anyway, their services always reminded me of a somewhat less-serious version of those youtube videos with the young child going through the motions of the Mass while his father chanted everything.

Those outside the Church aren't subject to canonical penalties for simulating sacraments. In regard to the Eucharist, the current Code of Canon Law has this to say:

The following incur a latae sententiae penalty of interdict or, if a cleric, a latae sententiae penalty of suspension:
a person who attempts the liturgical action of the Eucharistic sacrifice though not promoted to the sacerdotal order. (Can. 1378, §2)

Are ministers of non-Catholic churches "attempting the liturgical action of the Eucharistic sacrifice" when they celebrate what they call the Eucharist, the Lord's Supper, or Holy Communion? If so, then they are simulating a sacrament. If not, then I would argue that what they are doing is not objectively pleasing to God, even if they don't consider it a sacrament. Although it could be a misguided expression of sincere faith and devotion and, subjectively, even a means of grace, that doesn't change the fact that what they're doing is essentially a sort of parody of the Mass.

CCooze, I recently came across a Reformed (Presbyterian) article about why professing "one Baptism for the remission of sins" in the Nicene Creed doesn't necessarily mean one believes in baptismal regeneration. I didn't find the arguments convincing. The language of the Creed is the same as Acts 2:38. Catholics take our first Pope's words there at face value.

You are also far too harsh on people whose communities have been in schism for centuries. They largely don’t know better.

I agree. I'm sorry if I've come across as too harsh. My point is not to make a judgment against Protestants per se, but rather to argue why Catholics should not approach their rites as benign simply on account of their invalidity ("Well, they're not real sacraments anyway, so why does it matter?" etc.).

Did having paid musicians after the Second Vatican Council improve things? Is the problem of mediocre music a professional/amateur one or more related to American vs. other?

In the United States and in parish churches, I'm sure this is true, but not in Europe, Chapman.

Chris, I think that while music is mediocre everywhere, it is particularly American, though not exclusively, that mediocre or bad music is tolerated even in the cathedral churches. One can demand more of professionals, but quality liturgical music can be sung by people who are not being paid. I think you need to have both in a parish. I don't really have an explanation as to why a professional would sing music that is, well, what we have been largely subjected to in the last several decades. I understand why amateurs would do it if they never have been exposed to chant or never were formed well once exposed to it.

Lots of people here who don't know anything about Protestantism.

As the stipend was higher for a sung Mass, prior to VAT II, there was more work for organists in the Catholic church then there is today. It was a 7 day work week. It "cost" the church nothing since the organist/snger was paid a percentage of the stipend.

In my experience Sisters participation varied - teaching school was a primary job, running the convent (cooks & laundry) was secondary - then being sacristan, followed by teaching piano and then possibly playing the organ.

As the number of Sisters decreased the positions they vacated were filled by lay people.

It was EXTREMELY rare not to have daily Masses sung. Usually by one person playing the organ. I did it and after three years was able to buy a Baldwin Studio piano new...when I was 16. And I was one of two - the other organist did the 8AM Mass and most of the Sunday playing.

Someone, years and years and years ago said: Let's have SUNG MASSES with a higher stipend to better support the priest and also give us a secure music program position. Another brilliant move that VAT II ignored and destroyed.