Bug Report: Instrumental Doubles Up with AltVocal Offsets

[SpritersBlock]

Issue Checklist

• I have read the Contributing Guide
• I have checked the Issues/Discussions pages to see if my issue has already been reported
• I have properly titled my issue
• I did not have any mods installed when I encountered this issue

Platform

Windows (Downloadable Build)

Browser

None

Mobile Device Model

No response

Mobile OS Version

No response

Version

0.8.3

Description (include any images, videos, errors, or crash logs)

When playing Roses as Boyfriend but with Pico's instrumental, there are offsets applied to the instrumentals and vocals because Pico's version of Roses takes longer to start up.

"offsets": { "altInstrumentals": { "pico": -4000.0 }, "altVocals": { "pico": { "senpai-angry": 4000.0, "bf-pixel": 4000.0 } } },

However, this seems to apply some sort of duplication to the track, because you can hear what seems to be the instrumental doubling up with a slight offset, most notable in the beginning when the percussion starts to kick in. It doesn't seem to do it for the whole song, only for a small chunk at the beginning before seemingly going back to normal (or maybe it's just hard to tell).

2026-03-13.18-09-59.mp4

However, if you remove the data from altVocals, the instrumental plays normally.
"offsets": { "altInstrumentals": { "pico": -4000.0 }, "altVocals": { } },

2026-03-13.18-10-17.mp4

Notably, this doesn't happen when altInstrumentals' data is removed, only the altVocals.

I THINK this happens if you add the altVocal offsets to other songs too, but it's hard to tell. I did it on Fresh and I'm pretty sure this is also the case there based on the finger snaps sounding a little funky right before the notes start to come in about four seconds in (which I'm guessing is to do with the offset value being set to 4000).

2026-03-13.18-23-36.mp4

Steps to Reproduce

1. Playing as Boyfriend, play Roses with Pico's instrumental
2. Wait for the drums at the beginning of the song to sound... weird...
3. Navigate to assets/data/songs/roses/roses-metadata.json and remove the offset data in offsets/altVocals, then reload the game to hear the lack of weirdness
4. Alternatively, manually add altVocals offsets to other songs and hear the weirdness, particularly on songs with strong percussive sounds near the start

[Hundrec]

Nice catch! I discovered this as well sometime last year, so I can confirm this happens and needs a fix.

[NotHyper-474]

I remember trying to fix this once. It's harder than it seems to do, because it involves fixing up all this mess with the offset handling in PlayState and VoicesGroup, which would probably require a good rework.