When the first note of the sheet music is a grace note, I noticed that during playback, there is no sound on the first beat, and sound only occurs on the second beat.

[goodgame365]

Is there an existing issue for this?

• I have searched the existing issues

Current Behavior

When the first note of the sheet music is a grace note, I noticed that during playback, there is no sound on the first beat, and sound only occurs on the second beat.

20250728_182739.mp4

test file:
test.zip

Expected Behavior

Grace notes should be played quickly before the principal note, and playback should produce sound starting from the first beat to reflect the complete rhythmic effect.

Steps To Reproduce

The issue arises when the initial note in the score is a grace note.

Link to jsFiddle, CodePen, Project

No response

Version and Environment

alphatab 1.4 ~ 1.7

all browsers

Platform

Node.js

Anything else?

No response

[Danielku15]

Talking pure theory: This is somehow an invalid music sheet and by this I would say it is not directly a "bug". There are two kinds of "grace notes": On Beat and Before Beat.

"On Beat" grace notes steal their duration from the beat/note/rest afterwards.
"Before Beat" grace notes steal their duration from the beat/note/rest before.

In this file the grace note is a "before beat", but there is no beat or rest from which the grace beat could "steal" its duration. Due to this the grace note "slips" into a negative time axis and a "-1" measure which cannot exist.

To write this properly you likely need to add an anacrusis measure to your music sheet and add a rest there from which the grace note can steal its duration.

Talking technical feasibility: It should be possible somehow handle this special scenario. Some options could be

1. Convert the grace note as an "on note" in this case. (easiest)
2. Shifting the MIDI time axis by the required ticks (would need to be respected in repeats, metronome etc.)
3. Allowing negative MIDI ticks within alphaTab and handle it in all modules like export, external media etc.

[goodgame365]

GTP8 should be handled by the third option you mentioned. In fact, most of the scores read by AlphaTab are created using GTP8. Therefore, I personally believe that using GTP8 as the standard and resolving it through the third option is the best solution!