I searched for an english term for Durchhalteparole. 4 different online dictionaries (leo, dict.cc,...) - 4 different results
appeal to hold out,rallying call,exhortation to go on,call for perseverance
neither seems to be a common english term with fixed meaning and connotation similar to the german term. But thats not the question worrying me.
3 of 4 english terms just seem to be invented by these online translation services (probably literal machine translation). Rallying call might be the only real known english idiom i found on a smaller translation service, the other imo bad translations are from major services.
So what to do? Is there a known service which gives out only reliable translations, therefore yielding a smaller dictionary and less popular. Maybe backproofed by google ngrams or similar data. If you reverse translate the bad translation (Eng-Ger) funnily you get Durchhalteparole. So seems that these major services actually save these false-positives and spread them out and non native english people use them in a wrong context!? I know we exactly have Q&A for this cases, but hey thats the 21st century, is there really no reliable Ger-Eng dictionary for such standard terms?
on musikk comment. Here is some evidence

probably rallying call matches the meaning and connotation of Durchhalteparole, but i would have to ask on EL&U to be sure. I dont know how these terms can not be machine translated, otherwise there could not be 4 different term for one german fixed term with a fixed connotation. 3 have to be plain false imo
From Duden
Parole, die dazu auffordert, in einer [offensichtlich aussichtslosen] Sache um jeden Preis durchzuhalten
So im asking for translation services here, which at least state what the sources for their translations are (quality) or what the algorithm is. There are similar questions here.
Durchhalteparole? Can there really be 4 correct translations to a fixed term? imo not – Hauser Aug 15 '11 at 11:42Durchhalteparolehas a clear political connotation and in the dictionaries i searched only one, not several parellel translations. I can use any of above translations, but then it will not have the fixed connotation of the Duden, but it will literally be acall for perseverancewithout the connotation of being a hopeless call – Hauser Aug 15 '11 at 12:08