Please checke tempo meta event description - there may be a fault

[DF9TS]

In https://github.com/colxi/midi-parser-js/wiki/MIDI-File-Format-Specifications
the tempo meta event says: 0xFF 0x51 then 3 bytes for tempo value

When you check in other docs you will find it's 0xFF 0x51 0x03 then 3 bytes for tempo value
e.g. here https://www.cs.cmu.edu/~music/cmsip/readings/Standard-MIDI-file-format-updated.pdf

.. and my MIDI player crashes if I generate a MIDI file without the 03 in set tempo

[colxi]

Sorry for the delay, i've been very busy lately.
I'll try to take a look

[masi]

I cannot see a fault in the docs provided by colxi. For "set tempo" it says "length: 3" followed by the tempo. Perhaps you are missing that any mentioned length is represented by a byte value in the file. All meta events have a length byte following the type:

These events are defined by an event type value of 0xFF and have a variable size of parameter data which is defined after the event type.