Info on how to implement sustained notes

[Specy]

I have a music app that allows to "click" on notes to play them back like an instrument, and I wanted to add the possibility to sustain a note (for example a trumpet, violin, etc), I currently use the web audio API to play singular notes, and was going to use tone.js for the sustained ones.

I had some trouble looking online on what I could use to accomplish this, and also how to prepare the audio files for this.

I saw in the docs the Sampler and AmplitudeEnvelope which might be useful for this, most likely the sampler is the one I should look for.

Now the question is, how should the audio sprites be made? Is there a way I can separate the audio track into attack, loop, release and tell tone.js to use those, are there examples of audio sprites used for this (I was only able to find oscillators being used for sustained notes with tonejs)?

There is a lot of things that I don't know how to look for, just need some input on what to search/what to use to implement this