The mixer: functions to manually change volume / turn on or off each track

[CarlGao4]

Documentation confirmation

• I confirm that I have read the documentation and have not found an answer there.

Question

Is it possible to retrieve # of loaded MIDI tracks and change the volume of each track?

[spessasus]

Is it possible to retrieve # of loaded MIDI tracks

https://spessasus.github.io/spessasynth_lib/sequencer/#mididata

const trackCount = sequencer.midiData.tracks.length;

and change the volume of each track?

I believe you meant a MIDI channel. The entire MIDI file can consist of one track that handles all channels or multiple tracks, but each track can also handle multiple channels, there's nothing stopping it from playing to multiple channels. Therefore you can't control a volume of a track, but of a channel. A channel represents a single part i.e. instrument.

You can use controllerChange:

synth.controllerChange(channelNumber, midiControllers.mainVolume, yourValue);

Where channelNumber is your channel (starting from 0) and yourValue is the volume (0 - 127). I recommend using the provided enum midiControllers (shipped with core), but you can also use 7 for volume CC.

Also note that the MIDI file can change it too, so if you want to make it permanent, you need to lock the controller. Then when changing, you unlock, change, then lock again.

[CarlGao4]

First thanks for your explanation.
Actually, I meant MIDI track (mid only supports 16 channels, so some softwares use track to store music requiring more than 16 channels). I've just tried some Synthesizer functions and noticed that the SpessaSynth supports more than 16 channels (synth.addNewChannel()), so maybe I can modify the synthesizer to map each track to a specific channel?

[spessasus]

A track is just a list of MIDI messages, it doesn't have a channel. Even if there are 30 tracks, their voice messages still have to specify a channel, 0 through 15. And again, a track can use multiple channels, for example in MIDI format 0, but some files also use it in format 1. Adding more tracks doesn't get around the limit of MIDI.

If you want more channels, you need to make your MIDI file a multi-port MIDI.