Changing the Strings & Tuning
There are several online tutorials explaining how to change the strings on an oud. Here's a web page, and here's a YouTube video. There are also a number of sites, including the first link above, that list different tunings. What I haven't seen anywhere else, and what took me a while to realize, is what the benefits of different tunings are...why use one tuning instead of another? I'll try to address that and issues of Turkish written notation here.
Turkish vs. Arabic Tuning
The difference in actual concert pitch between Turkish and Arabic tuning is not difficult to understand. Turkish tuning is simply one whole step higher than Arabic tuning. So if the first (highest pitched) strings on an Arabic tuned oud are tuned to 'c', then on a Turkish tuned oud they would be tuned to 'd'.
The highest four courses of strings are always tuned in fourths on both Turkish and Arabic ouds. On Arabic ouds the tuning from the fourth to the first (highest pitched) course of strings is:
A, d, g, c
On Turkish ouds the tuning from the fourth to the first (highest pitched) course of strings is:
B, e, a, d
The two bass string courses are where different varieties of tuning are used in both Arabic and Turkish tuning. Probably the most common Arabic tuning today is:
C, F, A, d, g, c
The most common Turkish tuning is probably:
C#, F#, B, e, a, d
In addition to the above, there are other common tunings. In Arabic tuning 'D, G, A, d, g, c' is also used, and in Turkish tuning there is an equivalent 'E, A, B, e, a, d'. Another somewhat common Turkish tuning used by Necati Celik and his students, is 'B, F#, B, e, a, d'. So why use one tuning over another?
If you have an Arabic oud, are playing with Arabic musicians, or primarily listening to Arabic based makam music, then it makes sense to use one of the Arabic tunings. If you have a Turkish oud, are playing with Turkish, Armenian, or Greek musicians, or are primarily playing Ottoman/Turkish music, then it makes more sense to use one of the Turkish tunings. If you're only playing solo and are playing a mixture of Turkish and Arabic music, then it really doesn't matter whether you choose one of the Turkish or one of the Arabic tunings, as long as you get appropriate strings for that tuning and tension based on your oud. Using improper strings at too high tension can destroy your oud, so check with your oud maker if you're unsure which strings and tuning is right for your instrument.
Why choose a particular bass string tuning?
'C#, F#, B, e, a, d' for Turkish tuning is all in fourths. This is probably the easiest tuning for beginners, because movement from string to string is exactly the same on the entire oud.
'E, A, B, e, a, d' is my favorite Turkish tuning. Most common makams have a starting note of 'e' or 'd', and many use 'a' as the dominant note. If your bass strings are tuned to 'E' and 'A', then you can easily use those two open strings as a drone, echoing the most common notes in much of your music. With this tuning you can also easily lower the 'E' string to a 'D' when you're playing a makam that uses 'D' as the tonic.
'B, F#, B, e, a, d' is the tuning preferred by Necati Celik and his students. Why? Because he and his students transpose their playing a fourth lower (Kiz "tuning", in order to easily play with Turkish ney/flute players). So when most people would start a makam on the 'e', they would start on the 'B' instead. This tuning gives you the biggest range on your oud, and it allows you to have a low octave echo using the lowest bass string on one of the most common starting notes of makams, if you're playing a fourth lower. If you like the sound of playing lower tones, then this tuning can be a great choice.
'C, F, A, d, g, c' is the most common Arabic tuning. It has a nice wide range, the two bass strings are in fourths, and the following four courses are also in fourths. The gap between the 'F' and the 'A' is a third rather than a fourth, but this is easy to learn to play with. Because a number of makams begin on the 'C' on the fourth string (the 'A' string), having the lowest bass string tuned to a 'C' makes it easy to use as a drone for those makams.
'D, G, A, d, g, c' is currently my favorite Arabic tuning, for the same reasons 'E, A, B, e, a, d' is my favorite Turkish tuning. You have the most common drone strings as your open bass strings, and it's easy to drop the lowest bass string tuning down to 'C' when you're playing makams that have a 'C' tonic, if you'd like to do that.
There are additional less common tunings, but with the information above you should have an understanding as to the benefits of tuning your bass strings certain ways, either for ease of playing or to coincide with common notes of makams.
Turkish vs. Arabic Notation
Where it gets a little tricky is with Turkish written notation. Arabic sheet music is the same as Western sheet music in the sense that when you see a 'C' notated on a score you typically play a 'C' on your oud. With Turkish notation that is not the case. Turkish music is written a fourth above where it is typically played. So when you see a 'C' notated on Turkish sheet music you are actually going to play the 'G' beneath it on your oud.
Note: Particular makams in Turkish and Arabic music are nearly always written in the same key within each tradition, although different in each. For example, the makam Rast is always written in the key of G in Turkish notation, and the key of C in Arabic notation. But, in both traditions musicians can transpose on-the-fly and play in any key. More on that to come...
So what do you call a note that's written as a 'C' but played as a 'G'? It may not be accurate in terms of concert pitch, but I find it easier to refer to the note as it is written on the score. So if I see a note that is written as a 'C' on a Turkish score and I'm communicating with someone else who is looking at the score, I call it a 'C'. For me, it is too awkward to see a 'C' on the score but refer to it as a 'G'.
For tuning your Turkish oud, you need to use one of the above tunings and the actual concert pitches on your tuner. But for playing, what you read will not be what you are actually playing. This probably sounds more confusing than it will be in practice. In practice, you simply need to learn the string positions that correspond to the notes as they are written on sheet music. However, for tuning and for communicating with other musicians, it is important to understand that the music is notated and played differently. If you are playing Turkish and Arabic music from written notation, then you will need to learn to play from both, which is where it becomes rather difficult at first.
Turkish and Arabic Note Names
In Western music there are only seven note names (A, B, C, D, E, F, G). There are 12 possible notes per octave when you add in flats and sharps:
A, A#/Bb, B/Cb, B#/C, C#/Db, D, D#/Eb, E/Fb, E#/F, F#/Gb, G, G#/Ab
Turkish and Arabic music are different due to the micro-tones/quarter-tones they use. In Turkish music theory there are 53 possible notes per octave, and in Arabic music theory there are 24. In reality or performance, the micro-tones/quarter-tones are not fixed. Different musicians from different areas play them differently, and the pitches are raised or lowered at different points based on a number of factors.
Before Turkish and Arabic musicians adopted the Western notation system, they used unique names for every note. These names are still used today, but because music is written on the Western staff, either the Western note names or their solfege equivalents are more commonly used.
One good thing about learning the Turkish and Arabic note names is that unlike with Western note names and written notation, there is no difference between where the Turkish and Arabic notes are typically played on the oud. So for example, what is written as a 'G' in Turkish notation has the note name rast. This is written as a 'C' in Arabic notation, and is also called rast. The note rast is typically played on the third position of the fourth string on both Turkish and Arabic ouds. So, there is no conflict between what a note is called and where it is played if you use the original Turkish and Arabic note names.
Because there are a different number of notes in Turkish and Arabic music theory however, some of the names do not match, and additionally, some of the names are different.
Transposition in Turkish and Arabic Music
Although makams in Turkish and Arabic music are typically written in the same key all of the time, they can be transposed and played in any key. In Turkish music theory there are names for each transposition. They are referred to as "tunings", but in fact they are on-the-fly transpositions, as the tuning of the oud is not changed. The most common Turkish transposition is called Bolahenk, which is where the music is played a fourth lower than it is written, as noted above. Kız is the second most common transposition, which is played a seventh lower than written. In Kız if you see an 'A' written on a score you would actually play the 'B' below it.
In Arabic music transpositions are referred to as they are in Western music. Music that is written in the key of D is typically played in the key of D, but can also be played in any other key. When it is played in another key, it is simply stated as being played in that alternative key.
I'll end here with a quote from my oud teacher, Mavrothi Kontanis:
"When reading Ottoman scores, I don't see A, B, C, D, etc, I see Tonic, 2nd, 3rd, 4th, etc. I'm thinking about what makam I'm in, the intervals that occur within it, and where the melody is taking me at any given moment. Whether I'm in the key of E, D or B flat makes no real difference. The shape/intervals of the basic scale(s), and the seyir (melodic movement/development) are the most important things."
It will take time to get there, but that is indeed the ultimate goal.