Most of what you need to know has already been said, especially well by Romulo. (I can just about read/understand enough Spanish to suss out what he says!) I would add that in origin, a cran is essentially a substitute for a roll where a roll cannot be accomplished due to there being no lower pitch note available on the instrument to complete the second half (tap) of the roll.
In ITM a roll is an extended note that is rhythmically broken by brief visits to a higher note (a cut) and a lower note (a tap) within its duration. The precise pitches of those interrupting notes are not usually important as they are not part of the melody (or any harmony). Where the instrument does not allow a roll (e.g. lowest note) but a similar rhythmic, stuttering effect is desired, it may be achieved by a sequence of brief visits to different higher notes - a double or triple run of cuts. These cuts are not to specifically pitched notes, although some attempts to notate them may show them as such. It is usually virtually impossible to play them as written like that - the complex fingering changes do not allow the desired effect. Rather, one should just cut the finger indicated by the note name, with lower fingers still closing their holes; that note will not actually sound in tune or clearly, but it will break the main tone with a little âpopâ, and having those pops in the sequence at different pitches gives colour to the cran as well as being easier to do than a repeated cut to the same note (which would sound more like a trill anyway).
Crans were first used on the low D on Uillean pipes, and the technique has been adopted by flutes and whistles, and can also be used on 2nd octave D and on other notes (a la Highland pipes). It is also latterly imitated by some fiddlers where they encounter a similar technical situation, wanting to substitute for a roll where a note is on an open string, rather than executing a normal roll on the same pitch note fingered in a higher position on the next lower string. This fiddle usage is, I think, a nice pointer to the use of the cran - as an alternative, as a way of varying musical expression within the idiom.
Personally, I usually cran by cutting the bottom D to âAâ (L3 finger-hop), then to âGâ (R1 finger-hop) [and sometimes, depending on note length and required rhythm, to âF#â (R2 finger-hop) as well], thus - (xxx xxx)
(xxo xxx)
(xxx xxx)
(xxx oxx)
(xxx xxx)
[(xxx xox)
(xxx xxx)]
Note that the RH fingers stay down on their holes throughout save when actually cutting.
For a second octave cran, I do this exactly as for bottom D crans save that L1 is raised throughout. This produces a sequence of cuts to a variety of indeterminate-pitch notes in the region of the C natural below, which hardly matters â the desired effect is the staccato stutter breaking up the long D. [One can also keep L1 down and simply overblow the bottom octave cran, which does achieve cuts to higher notes, though with a rather over-toney sound, if preferred (not by meâŠ.).]
Like everything else, playing crans effectively requires relaxed control, not strained tension. Practise the fingering shapes slowly to begin with making sure you retain relaxation in the fingers as you speed up as the sequence becomes familiar.