Matzouka, Trebzon, 1950s (source).
After the Cretan lyra (and its cousin on Karpathos!), as well as various types of kemence bowed lute (some of which feature in my post on Indian and world fiddles), the music of the Pontic lyra is also most beguiling.
Along with the Greek populations along the Aegean coast, centred on the port of Smyrna, the Greeks of the Black Sea also had thriving traditions, which suffered just as grievously from the devastating conflicts that led to the population expulsions of 1923. 
From Bruce Clark, Twice a stranger.
Instruments make a partial entry-point into regional cultures. For the wider musical setting, as ever, the Pontic lyra accompanies the singing and dancing of social musicking (parakathi or muhabeti),  with additive metres prominent. So far I’ve had more luck finding audio recordings than video footage in folk context (although the tributes below from the Union of Pontic Youth of Attica have some fine images, both still and moving). From east to west, the sub-regions of the Pontos also show distinct musical cultures.
This recording of the music of emigrants from the Bafra district of Samsun was made soon after the expulsions:
And this playlist of traditional songs and dances of Bafra was issued in 2001 by Radio Trapezounta Boston, whose YouTube channel has a wealth of material:
Most of the musicians featured below were relocated to Greece and the diaspora, or were born there.
The Union of Pontic Youth of Attica has uploaded tributes to some of the great masters of yesteryear—including Giorgos Petrides (1917–1984) and Chrysanthos Theodoridis (1905–2001):
Giorgos Kougioumtzidis (1935–2007) and Christoforos Christoforidis (1905–2001):
Yiannis Tsortanidis (1900–1983) and Sevastidis Pantelis (1922–89):
Stathis Beniamidis (1920–95) and Apostolos Athanasiadis (1907–76):
Nikos Papavramidis (1907–95) and Christos Bairaktaris (1905–81):
He is also heard here:
Ilias Kementzides (1926-2006) was born in Kazakhstan after his parents were expelled from Samsun; in 1940 he moved to Greece, and in 1974 to the USA. Here’s a short film, with clips of him playing for the Pontic Society in Queens, New York:
Ilias Yfantidis (b.1976) was born in Athens. There are further links on Samiou’s page for him, including
Tsakalidis Kostikas (1933–82) was born in Drama, northeast Greece (see e.g. Bruce Clark, Twice a stranger, pp.75–82), where his parents had been relocated from Trebizond. Among tracks from this playlist is:
Activity doubtless continues in the Black Sea homeland (where the lyra became known—to Turks—as kemence), even if it has been much attenuated. The image from the 1950s at the head of this post is attractive, but would need further documentation before we could assess its relevance: does it show performers of the Pontic Greek style?
I’d like to find audio-video material (perhaps it requires a more informed search), but in the majority Turkish culture, Pontic Greek traditions there were doubtless under a cloud until the belated thawing of Greek–Turkish relations. Even then, in 2002 the Trabzon folklorist Ömer Asan was charged with “propagating separatism” for his book Pontos Kültürü (cf. the Armenian trials soon after). More recently, the work of anthropologist Nikos Mahailidis (Soundscapes of Trabzon: music, memory, and power in Turkey, 2016) will offer clues:
In Turkey, the enterprising Kalan Müzik has issued two archive CDs of Pontic refugees Pontus Şarkilari, featuring Yannis Haralambidis and Athina Korsavidou (here as playlists):
Lastly, an evocative clip of the Pontic bagpipe angeion (touloumi) at a parakathi gathering at the Association for Pontic Greeks in Cologne, 2012:
 For a recent thesis, see Ioannis Tsekouras, “Nostalgia, emotionality, and ethno-regionalism in Pontic parakathi singing” (2017), citing much further reading. Earlier, Matthaios Tsahouridis— himself an experimental virtuoso on the Pontic lyra (YouTube topic)—wrote his thesis The Pontic lyra in contemporary Greece (2007).