Once the oud has been strung, you need to decide on which tuning to use. This will depend on the type of music you want to play, and may be influenced by a famous oud player or the recommendations of your oud teacher. I shall outline some common tunings used in the Arab and Turkish schools of oud playing, and then discuss the tunings selected by some great oud players.
I have used the following pitch notation below. Each pitch is labelled with a name (C, D, E, etc.) and an octave number as a subscript (1, 2, 3, etc.). Higher numbers indicate higher octaves, and in this notation it is conventional to write middle C as C4.
The most common Arab tuning is (low to high):
The use of F2 instead of G2 is also very popular, and the 6th string is often tuned to C2 for maqamat based on C. Alternatively, many players from the Iraqi school prefer to place the 6th string next to the 1st string, e.g. Munir Bashir and Jamil Ghanim both used the tuning C3D3G3C4F4F2 and Jamil Bashir used the tuning D3E3A3D4G4G2.
When reading Arab or Western sheet music you should bear in mind that the oud (like the guitar) sounds an octave lower than it is written. This means, for example, that if the highest string is tuned to C4 (middle C) it will be notated as follows:
One of the most common Turkish tunings, also known as the 'Bolahenk' tuning, is (low to high):
where the symbol is explained here. A variation on this tuning was used by Şerif Muhiddin Targan: D2A2B2E3A3D4.
Things become complicated when it comes to Turkish sheet music. Firstly, Turkish music is conventionally written a fourth higher than Western music, so that middle C on a Western sheet will appear as the F above middle C on a Turkish sheet. Secondly, you have to remember that the oud sounds an octave lower than it is written in Western sheet music. The combined result is that if the highest string of the oud (1st string) is tuned to D4 (D above middle C) as in the Bolahenk tuning above, it will be notated on a Turkish sheet as follows: