⇒ When nearly perfectly synced with a media player, the timer in Furnace seems to slowly drift behind. VERY slowly, at least on the Mega Drive. Further investigation necessary, with a focus on other systems.

⇒ Sometimes, when playing from the middle of a song, Furnace underestimates how much time would have already passed. Maybe it's the song tempo? Maybe the chips involved?

Issue seen with these (all my covers - should I list demo songs instead?)...
Atari 2600/7800 (60Hz) • TIA ——— Bad Apple!! (sp 6, vt 138/150)
Mega Drive • YM2612 + SN76489 (60Hz) ——— Cab — Angel With A Shotgun (as seen in the video) (sp 6, vt 124/150)
Mega Drive (60Hz) ——— Bad Apple!! (sp 6, vt 138/150)
Master System w/ FM • SN76489 + YM2413 ——— Cab — Angel With A Shotgun (sp 6, vt 124/150)
NES • 2A03 ——— Michael Jackson — Smooth Criminal (sp 6, vt 120/150)
NES — WORLD 1-1 (sp 1, vt 100/150) (FAR off)
Game Gear • SN76489 ——— Michael Jackson — Beat It (sp 6, vt 138/150)
Game Gear ——— Evanescence — Bring Me To Life (sp 3, vt 96/150)

Issue NOT seen on...
Commodore PET (50Hz) ——— Bad Apple!! (sp 6, vt 138/125)
2x AY-3-8910 (60Hz) ——— Bad Apple!! (sp 6, vt 138/150)
Mega Drive (44Hz) ——— Linkin Park — Shadow Of The Day (sp 6, vt 150/150)