I've heard it said that Martin Luther condemned the use of pipe organs, saying that they were somehow evil.
What is the source for this quote? Or is it falsely attributed to Luther?
Might this be your quote?
"The organ in the worship is the insignia of Baal" (Martin Luther, Mcclintock & Strong's Encyclopedia Volume VI, page 762)
This phrase turns up 1,400 results in Google; but it may not be accurate.
One researcher, apparently familiar with Luther and this quote, had this rebuttal:
Strong DOES NOT use the word “insignia,” it uses the word “ensign!” Various other church of Christ denomination websites also misquote this statement.
Searching Google for the quote with "ensign" instead of "insignia" turns up 7 results. This suggests widespread dissemination of the (mis)quote without checking sources. (This is possibly the encyclopedic source, though it's certainly not word-for-word; thanks @James T)
The source mentioned above had more to say on the topic:
One big problem with this quote is that students of the writings of Luther CANNOT find this quote ANYWHERE in the writings of Martin Luther! It is well known that Martin Luther DID NOT oppose musical instruments in church. Luther was at odds with John Calvin on this subject. Luther taught Gospel Liberty, that anything not specifically condemned in the New Testament was authorized.
With a creative search query, I determined that 98% of the online sources for this quote reference the same Martin Luther encyclopedia referenced above.
Another possible source for this saying is Heinrich Eckhard's Fasciculus Controversiarum Theologicarum where he states,
Lutherus organa Musica inter Baalis insignia refert.
Which a 19th century author translates as:
Luther considers organs among the ensigns of Baal.
A few problems, though: @James T's source suggests that "organa Musica" is better translated as "instruments of music." Further, Eckhard isn't even himself the original source of his statement.
As we trace this quote back, we go from one shaky source to another (as the "quote" changes) until the internet trail peters out at "Anhaldini p. 74"
Then he perceives with great clarity what great fools they all are who want to become pious through works, and he will not give one penny for all the tonsures of priests, monks, bishops, and popes nor for cowls, incensing, ringing of bells, burning of candles, singing, making noise on the organ, and reciting prayers with all their external performance. He sees how all this is nothing but idolatry and foolish sham, exactly as the Israelites worshipped Baal Ashtaroth and the calf in the desert, a precious matter under the influence of the old light of their self-willed and egotistical reason.
Luther, M. (1999). Luther’s works, vol. 52: Sermons II. (J. J. Pelikan, H. C. Oswald, & H. T. Lehmann, Eds.) (Vol. 52, pp. 79–80). Philadelphia: Fortress Press.