The Bayati scale is a heptatonic scale that can be built using the following steps between notes: ¾, ¾, 1, 1, ½, 1, 1.
This is an Arabic scale that uses quarter tone intervals. If we use (b/2) to denote a quarter note flat (a drop by a quarter tone), then one example of the Bayati scale would be A, B(b/2), C, D, E, F, G. This example is shown below in traditional notation (the horizontal line through b denotes a drop by a quarter note) and in guitar tablature notation (to the extent that guitar tablature allows quarter notes).
One way to obtain this scale is to and to drop the second degree of natural minor scale by a quarter tone. The example above is the natural minor scale in A with B lowered by a quarter tone.