From a Gramophone Magazine review of the Prima Voce release -
"Herold, who made 200 recordings over 42 sessions, was a legend in his lifetime in his native Denmark, and was also much sought-after in other European centres.
Apparently a singing actor of considerable force on stage, he was a tenor who evinces on this reissue a sense of concentrated intensity as the basic tenet of his style. He was also, stylistically, a well-endowed artist who had the attributes of his age: firm, even tone throughout his range and an innate sense of line and phrasing.
French-trained, his voice shows remarkable similarities with that of his great French coeval, Paul Franz. You can judge the likeness by listening to one of the few items here sung in the original language, that from Le cid, where Herold exhibits in the recitative a rewarding nobility and sincerity recalling the French tenor’s manner.
Both singers also share a quite remarkable control of breath so that Herold, in an exemplary “Celeste Aida”, sings seamlessly through phrases that other singers are forced to break, and at the end he proves that it is quite possible to sing the final B flat piano. Not only does he do that but he holds the note and fines it away to nothing.
Herold has a voice that hovers between the lyric and heroic, the topmost notes not reached without some effort.