fernandraynaud - 5-7-2010 at 01:10 PM
I wonder if others all have this experience.
Before I play I check the oud's tuning by harmonics on D, G and C strings, or with my iPhone.
BTW this little $0.99 tuner is fantastic, almost worth getting an iPhone for, and it is fast enough so you can use it to improve your fingering. It
shows Frequency in Hz, and microtuning intermediate notes very well.
http://www.youtube.com/watch?v=0A2o_jymFd8
What I find is always the oud's metal wound strings are quite stable, and the two nylon courses have risen, say 25-50 cents. I don't think they have
dropped in pitch more than a couple of times.
On my harpsichord changing weather brings falling OR rising tuning, wood is a humidity sensor, and different structures stretch and shrink. It's often
tempting to just wait for the opposite trend rather than tune 57 strings. 
The clavichord is incomprehensibly stable. Good thing, given the 118 tuning pins 
Guitars and basses rise and fall. Only the nylons on my ouds almost always rise!
Does anyone understand this?
Do people have mostly rising or falling strings?
Luttgutt - 5-7-2010 at 01:22 PM
Never raising... mine just fall a litle when I take the oud out.
P.s. humidity in Norway is around 40 in the summer, 20 in the winter.
fernandraynaud - 5-7-2010 at 01:42 PM
I would expect slight falling from peg slippage and I'm puzzled. We have relatively steady humidity by the Pacific.
Since the metal-wound strings don't change much, I wouldn't think the oud's structure is what is changing (as it is on the metal-strung harpsichord).
So it's the nylon.
I had thought nylon was a plastic without a lot of interaction wth water, but it's hygroscopic, absorbing 8% of its weight in water. It swells when
damp, and becomes heavier? so pitch drops when humidity rises?
And as I look at some charts, our steady humidity is apparently a myth. I see that percent humidity here in the last 24 hours fluctuated from 22 to
77%.
A possible explanation is that there is a daily cycle, and that I tend to pick up the ouds at a certain time of day. I'm digging into historical
data.
I wonder how many people have consistent rising or dropping only on the nylon strings?
Sazi - 5-7-2010 at 04:25 PM
I had exactly the same phenomena when I played Turkish oud with nylon strings, the oud was like a barometer, the trouble is you only have to re-tune
it back again later when the humidity changes again.
I don't have that problem any more using PVF trebles, and won't go back to nylon.
I've been watching the humidity lately as I'm doing some soundboard work and repairs/rebuilds using hide glue, and there does seem to be daily cycles
and also even a very slight breeze from an open window can change things.
ameer - 5-7-2010 at 06:07 PM
I've had strings rise a bit I think but they mostly fall in pitch here in the southeast. A lot of times a course will slip equally; the strings will
be perfectly in tune with each other but they've dropped a halfstep or so.