Allen MOS-2 Tuning Helps!

[myorgan]

Folks,

I hope y'all don't mind me sharing my experiences tuning my MOS-2 505B today. Maybe it'll help someone else.

Last fall, the tuning of my 505B's B-computer slipped. Since the church where I have the organ was closing for the winter (and because I couldn't find a time without screeching children), I just got it close and forgot about it for the winter.

Now that the church has been open for the last month, I have been dissatisfied with the organ when comparing it to the church service earlier each Sunday, where I have my ADC-4300, but couldn't figure out why. Today, I waited the extra hour after the service ended at 12:30, and tuned it using a tuner on my iPad.

At first, I tuned using the Great 8' Prinzipal and A-440. Things didn't sound like they should have when I was done, so I tried Middle C with the same stop. Finally, I remembered that pipe organs are sometimes based on the Great 4' Octave, so I tuned each computer separately, then together to that stop.

WOW!!! I can't believe the difference. For the last month the organ has sounded like some other company's attempt at replicating a pipe organ sound, but ending up with lackluster Flute Choruses, Prinzipal Chorus, Celestes, and Reed Chorus. Nothing sounded right. Now, the organ, in spite of carpeting and suspended ceiling, sounds like a pipe organ should. The ensembles are back, and I couldn't resist playing the organ for the next two hours to experiment with the "new" organ at my disposal.

It was definitely worth the time to retune the organ, and I feel like I now have a whole new organ to play with.

Michael

[Admin]

Here are Allen's tuning instructions for the 505

1. Tune Computer "A" to A-440 ("B" computer off)
2. Depress Great Prinzipal 8 and Chorus Tuning. (both computers on)
3. Hold A5 on the Great Manual
4. Tune Computer "B" sharp (clockwise) five beats per second.

[myorgan]

Here are Allen's tuning instructions for the 505

NOW YOU TELL ME!!! Where were you when I needed you?;-)

Needless to say, I didn't know about the Chorus Tuning. That must be how the tuning variations mentioned below are turned off. To clarify, A5 with the Great Prinzipal 8' is actually played one octave above A-440 (A-220)--assuming the lowest A on the piano is A0? A-440 would actually be A4, correct?

For the first time, I was able to directly observe stretched tuning and equal temperament. When I tuned to A-440, I noticed that middle C was a couple of cents sharp (or flat--I can't remember). I also noticed that when a note was held, the tuning varied by a cent or so while held. In previous trips into the back of the organ, I thought I saw a chip with Random Motion on it. I know that was something introduced in the earlier analog Allens, but didn't realize it continued into the MOS era. Even if it did, I thought there was a way to turn it off, but I haven't found it yet--must be the Chorus Tuning.

I didn't get any documentation with this organ and had to purchase my own manual, but I don't remember the tuning instructions being part of the owner's manual (probably in the Service Manual). Oh, well.

Thanks so much for the clarification. I'd imagine the same instructions hold true of the 305, 505, 705, 805, 1105, and 1405 series as well. I probably should have searched here first.

Thanks again.

Michael