In this video I demonstrate how to apply a common oud technique, where notes are played using the same finger with a slight slide between them.  In ‘classical’ terminology this may be called portamento or glissando, but the way that this is used in Arabic oud playing is much more specific than those general terms imply.  So we can think of this perhaps as a sort of special case of portamento/glissando.

This sound is frequently used in maqam rast, hijaz, bayati, and jiharkah.  In the video, I go over various examples of each, drawn mainly from the playing of Farid el-Atrash, Simon Shaheen and George Michel - all fantastic oud players that are required listening for any serious student. 

In several instances, it's possible to choose a different finger (i.e., play with the 1st or 2nd finger, or to play with the 3rd or 4th finger). In the beginning, I would suggest sticking with one option until you feel fairly comfortable rather than trying to learn both options right away.