As historical instruments, there is no standard for stringing replicas of the old Gaelic harps, and no original stringing regimes survive with the instruments. These notes here are the results of my practical experiments and serve as a guide to stringing the three different types of Gaelic harp: "high headed", "large low headed" and "small low headed". If you need detailed stringcharts or supplies of wire please visit the Emporium.
High headed Gaelic harps (dating from after about 1650) maintain a fairly consistent scaling from the treble down to the bass, and this allows stringing with one metal, usually yellow brass, as described by the 19th century informants (see history). To maintain a consistent sound and feel across the range of the instrument, the strings are graded in thickness, with the treble strings thin and the basses thick. Exact gauges depend on the precise tuning and dimensions of the harp, but I would suggest that 0.48mm in the treble and 1.1 or 1.2mm in the bass would be a typical arrangement. The treble is proportionally more sensitive to the length and pitch relationship, so the harp should be pitched from the treble string lengths. If this leads to an uncomfortably high or low pitch to the instrument, then iron can be tried in the treble, or the string configuration can be changed (which pin joins to which shoe). Assuming we are dealing with a measured replica harp we should be unlikely to need to follow Arthur O'Neill's account and have the harp "taken asunder, as when it was tuned the treble was thought to be too long", but it is worth inspecting the original critically to see if old repairs or misguided restorations have affected the scaling.
The bass tuning is worth mentioning. The note g below middle c will of course have two strings tuned to this pitch, known as comhluighe. Then there will be a diatonic octave below that, and then it seems usual to start missing pitches from the bass. When there is a gap at F an octave below comhluighe, the E string is known as
Tead leagtha (fallen string); if that string is raised to F it is called Tead leagaidh (falling string). There is evidence that B strings were mised out below this too. One can make the sub-bass range entirely pentatonic, but I would suggest arranging the presence and absence of F and B strings to allow the lowest string of the harp to be either C or G.
See my tutor book for more info on tunings.
Large low-headed harps were made during the 16th century, up to about 1650. Their scaling is comparable to that of the later high-headed instruments, except that below the midrange the scaling falls off somewhat so the bass strings are 3/4 to 4/5 of their minimum ideal length, meaning that if strung with brass down into the bass the lowest notes will sound dull and twangy. James MacDonnell in the early 19th century compared the sound of Patrick Quin's large low-headed harp unfavourably with Rose Mooney's high headed instrument.
To allow short bass strings to sound well we need to increase the density without increasing the stiffness; and unless we use un-historical wound strings we are faced with using softer and denser metals than brass. Silver is mentioned as a string material at this date and works very well in the lowest octave or so.
So we end up with a string regime using 0.48mm brass in the high treble (soft iron can be substituted if the treble strings are too long for brass). At some point - maybe at comhluighe g; maybe lower, the metal can switch to silver; I would suggest 1.2mm as a thickest wire for the lowest strings.
As mentioned above the harp should as a matter of course be tuned with comhluighe g, and with a gapped bass below cronan G. The treble and mid-range scaling should be used to pitch the entire instrument. I would expect at least three strings below cronan G.
The three surviving medieval instruments of the small low-headed design have a scaling that is even slower than the later large low-headed instruments. The scaling falls away from the midrange so the bass strings are around 2/3 of their ideal length. If a small low-headed instrument is strung in brass from treble to bass, then when the treble strings are about to snap, the basses are so dull and slack that they barely sound a pitch.
It is certainly possible to string a small low headed harp successfully using brass for the treble and mid range and silver for the lowest octave or so. However this is not ideal as silver is not dense enough to sound good at these lengths and pitches, and such a regime is best reserved for student instruments where budgets are tight.
The ideal stringing for a small low headed harp is undoubtably brass in the treble and upper mid range, and gold in the bass. Silver can if desired be used for the lower mid range between the brass and gold, or lower carat gold can bridge the gap instead.
Because of the speed with which the scaling falls away, the changes in metal required and the different ways that this can be achieved means that there is an almost unlimited scope for experimentation. Unlike with brass and iron, which is commercially produced as historical music wire, gold and silver need to be acquired as the raw material from bullion supply houses or jewelers, neither of whom are likely to have much understanding of or interest in the physical properties of the wire relating to its use under tension. The successes so far in stringing harps with gold and silver are the result of complex series of experimental stringings over a number of years by a few pioneer harpers, namely Ann Heymann in the USA, on whose work my own efforts are based. Though it is tempting to insert data on gold and silver into the standard stringchart formulae, the number of variables in alloy and hardness, and the more subtle behaviour of these metals stretching and work-hardening under tension mean such a reductive approach is not ideal. Indeed, different batches of nominally identical wire from the same supplier can behave differently when on the harp. The goal after all is quality of sound, so measurement and calculation must go hand in hand with critical listening and aesthetic judgement.
The work is expensive and slow; and we welcome wider interest in trying these exciting materials on various replica harps - our ongoing experiments can only benefit from your participation, interest and custom! Contact Ann in America or me in Scotland; we can discuss your budget and harp, and recommend or supply appropriate gold and silver wire for that instrument, on either a more conservative or more experimental basis.
The above comments apply to accurate measured replicas of the old Gaelic harps, replicas which preserve the pin and shoe positions of the originals such as David Kortier's Student early Irish harps. If a modern harp maker deviates from the historical design, even just by re-arranging or modernising the stringing, then the issue of designing a string regime changes completely.
Modern "wire-strung" harps, such as the popular models by Triplett, Ardival, George Stevens, or modified historical designs such as those by Jay Witcher or Frank Sievert are best strung according to the makers intentions.