I have already argued that Scottish English is a bipolar continuum, and thus to describe the phonology of this continuum we need, at least descriptively, to refer to the phonologies of the two ends, Scottish Standard English and Scots. Both systems share inventories of vowels and consonants, but differ in lexical incidence, that is in the way that they are distributed across the lexicon. This results from the different historical developments of the two varieties. In fact, for the majority of the lexicon, lexical incidence largely overlaps, so we can recognize common or shared vowels, e.g. KIT/BIT, or consonants, e.g. /l/, which differ only in having distinctive (and sometimes overlapping) realizations in Scottish Standard English and Scots. Those speakers who have access to the Scots end of the continuum may also use particular Scots realizations for certain words, e.g.  for  in house, and so have a distinct system of Scots lexical incidence. Recent research based on recorded interviews and conversations reveals that the actual number of words involved in Scots incidence is small, and their overall frequency is low (Stuart-Smith 2003), though the actual frequency may be higher in unobserved vernacular speech. Using the Scots variant is strongly marked both for speaker and hearer in the Scottish context.

This division into Scottish Standard English and Scots systems inevitably presents an over-simplistic picture when we look at Scottish English speech. There are certainly speakers who use Scottish Standard English more or less exclusively. But there are far more who have access to Scottish Standard English, but who also have access to Scots, and who drift between the two, and this is especially common of those living in the Central Belt. What this means in practice is that there is a large number of Scottish English speakers, of working-class background, either still working class or recently moved into the middle classes, who may use distinctive Scots variants for most words, but who may alternate to a Scots variant for a smaller set of Scots words. Describing the phonological behavior of these speakers, who seem to use systematically an alternating system of vowels and some consonants, presents quite a challenge to phoneticians, phonologists and sociolinguists (Stuart-Smith 2003).

The phonetic and phonological description that follows owes much to previous work which is difficult to supersede and where many more details and extensive further bibliography may be found. Relevant works include Abercrombie (1979), Aitken (1979, 1984), Johnston (1997) and Macafee (1997). Particularly useful studies for Edinburgh, and for Glasgow, which is the accent used as the example for the tables and generally for comments unless noted, include Chirrey (1999), Johnston (1985), Macafee (1983, 1994), Macaulay (1977), Johnston and Speitel (1983), Romaine (1978) and Stuart-Smith (1999, 2003). The source of my comments on Glaswegian largely derive from analysis of a recent corpus of Glaswegian collected in 1997 by me with the help of Claire Timmins, a Scottish fieldworker and researcher.