Following tigger's idea from #12, here is a link to the Mozarteum's transcription of Martin's friend's letter:
https://dme.mozarteum.at/DME/briefe/letter.ph...
A pdf of the entire letter @ https://dme.mozarteum.at/DME/objs/raradocs/tr...
and the Mozarteum's English translation (also in pdf format): https://dme.mozarteum.at/DME/objs/raradocs/tr...
The passage is given as follows:
einer nent sich otini, welcher
nicht übel singt, aber halt schwer, wie alle italieniς
Tenore, und ist unser sehr guter freünd, der andere weis
ich nicht wie er sich nent, er ist Jung noch, aber nicht viel
rares. primo ballerino. gut. prima Ballerina: gut,
und man sagt, sie seÿe gar kein hund nicht, ich
aber habe sie zwahr in der nähe nicht gesehen, die
übrigen aber wie alle andern: Ein Crudescer ist da
gewesen, der gut springt, aber nicht so schreibt
wie ich: wie die säü brunzen.
[S. 3]
das orcchestro, ist nicht übel gewesen.
Given the credentials of the Mozarteum, it seems very unlikely that this - brunzen vs. grunzen - is a simple misreading of Mozart's handwriting. According to the information available on its website, the editors there address this exact problem as follows:
EDITIONSRICHTLINIEN
Offensichtliche Schreibfehler werden durch eine gepunktete Linie, unsichere Lesarten durch eine gestrichelte Linie unter dem entsprechenden Wort angezeigt.
The passage in question is not marked in any way. The Richtlinien are quite extensive; the quote above is only a small excerpt.
The English translation is given there as: There was a crudescer 15
there, who leaps well, but does not write like I do: the way pigs piss.
where note 15 states that Mozart intended "grottesco".
Online transcriptions/digitizations vary greatly in quality and most of them are pretty poor in my experience. Quality translations are often behind a paywall and that's a good thing. Mistakes in OCR have already been pointed out. There are also other errors that can occur during the digitization process. Although it is understandable, the translation cited in #14 doesn't seem to be of the best quality.
Would a "b" be misread for a "g"? I suppose anything is possible, but the letter "b" goes above the middle line and does not cross the baseline. A "g" goes under the baseline and does not go above the middle line. Seems unlikely to be confused. Unfortunately the Mozarteum website does not include a facsimile of the original letter in Mozart's hand. They do, however, cite their source: Erich H. Müller von Asow, Briefe Wolfgang Amadeus Mozarts, hrsg. mit Originalbriefen in Lichtdruck, for anyone who is interested.
Sorry if this is all a little off-topic, but it is interesting, what the link in #12 yields.