from Edward Bunting, The Ancient Music of Ireland (Dublin 1840), page 22: The strings of the harp.
Irish freagradh téad na bhféith eolach
spoken by Gráinne Yeats
Scottish Gaelic freagairt teud nam fèith-eòlach spoken by Tony Dilworth
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Freagrach tead na feitheolach - Response to leading sinews
Since freagrach must clearly mean 'a response', it is likely to be an error for freagradh, an acceptable variant of freagra, 'an answer', the string, as Bunting tells us in his foonote, "Being octave below the string of melody" (see Tead na feitheolach and Fhreagrach).
Colm Ó Baoill 2002
The ms12 chart gives ‘freagrach’ as the name of this string, though the chart may be indicating that all of the bass strings between comhluighe and cronan may be referred to as freagrach.
Simon Chadwick 2008