Analysis of information sources in references of the Wikipedia article "Pitch-accent language" in English language version.
Both Latvian and Lithuanian are pitch languages. In Lithuanian, stressed long vocalic segments (long vowels, diphthongs, and sequences of vowel plus sonorant) show a distinctive opposition of rising and falling pitch, cf. kar̃tų 'time:gen.pl' vs. kártų 'hang:irr.3'. In standard Latvian (and some of the dialects), long vocalic sequences (of the same type as in Lithuanian) distinguish three varieties of pitch: 'even', 'falling', and 'broken' ('broken pitch' being a falling pitch with superadded glottalisation). They are fully differentiated in stressed syllables only: unstressed syllables have an opposition of glottalised and non-glottalised long vocalic segments. Segments with 'even' pitch are ultra long. Neither Lithuanian nor Latvian mark pitch in their standard orthography.
(..)what is the historical relationship between the Livonian stød and the identical or at least very similar "Stosston" intonation of the coterritorial Latvian language? Almost certainly one of them got it from the other. The languages have influenced each other in many ways, in both directions. But which way did the influence go in this case? Scholarly opinion on this question is divided. Thomson (1890: 59) and Kettunen (1925: 4) thought that Livonian had borrowed the stød from Latvian, whereas Posti (1942: 325) thought that Latvian got it from Livonian. My conclusion that the Livonian stød is a tonal feature is more consonant with the former view. Livonian is the only Finno-Ugric language known to have a tonal or pitch accent, while it is a feature of several branches of Indo-European, including Balto-Slavic in particular. On the hypothesis that Livonian got its stød under the influence of Latvian, we account for the Livonian stød by language contact, and for the Latvian stød as a Baltic inheritance.