# Support hacky user-assigned music through Programmer Instruments

**URL:** <https://qa.fmod.com/t/support-hacky-user-assigned-music-through-programmer-instruments/23852>\
**Category:** Unity\
**Tags:** unity, csharp\
**Created:** [December 30, 2025, 2:06am UTC](https://qa.fmod.com/t/support-hacky-user-assigned-music-through-programmer-instruments/23852 "2025-12-30T02:06:38Z")\
**Posts on this page:** 1\
**Showing post:** 2

<div class="post-metadata">

**Author:** ![Connor\_FMOD](https://yyz2.discourse-cdn.com/flex036/user_avatar/qa.fmod.com/connor_fmod/32/3685_2.png) [@Connor\_FMOD](https://qa.fmod.com/u/Connor_FMOD)\
**Post date:** [December 30, 2025, 5:20am UTC](https://qa.fmod.com/t/support-hacky-user-assigned-music-through-programmer-instruments/23852/2 "2025-12-30T05:20:04Z")

</div>

Hi,

Thanks for the photos.

This is definitely possible! I have slightly modified our scripting example: [Unity Integration | Examples Programmer Sounds](https://fmod.com/docs/2.03/unity/examples-programmer-sounds.html). When we assign the event callback ([FMOD Engine | Studio Api Eventinstance - Fmod::Studio::Event::Callback::Type](https://fmod.com/docs/2.03/api/studio-api-eventinstance.html#fmod_studio_event_callback_type)) `CREATE_PROGRAMMER_SOUND` this will trigger both times the programmer instruments are played. I made an event similar to yours:

 ![image](https://canada1.discourse-cdn.com/flex036/uploads/fmod/original/2X/5/5e03a4f9acfcd6de022aff449246b88e07f028cd.png)

Where the fader of each audio track is controlled via a parameter.

I then use the following script to play and assigned the audio files for both the programmer instruments:

```csharp
using System;
using System.Collections.Generic;
using System.Runtime.InteropServices;
using UnityEngine;
using UnityEngine.InputSystem;

[Serializable]
public class EventData
{
    // Paths of the audio files on disk to be played
    public List<string> paths = new List<string>();

    // Used increment the file paths used when triggering the programmer instruments
    private int currentProgInstrument = 0;
    public int CurrentProgInstrument
    {
        get
        {
            return currentProgInstrument;
        }
        set
        {
            currentProgInstrument = value;
        }
    }
}

public class TriggerTwoProgInstruments : MonoBehaviour
{
    public FMODUnity.EventReference eventRef;
    private FMOD.Studio.EventInstance eventInst;

    public EventData data = new EventData();

    void Start()
    {
        // Create our event instance
        eventInst = FMODUnity.RuntimeManager.CreateInstance(eventRef);

        // Set our callback that will only trigger when the programmer instruments are created and destroyed
        eventInst.setCallback(EventCallback, FMOD.Studio.EVENT_CALLBACK_TYPE.CREATE_PROGRAMMER_SOUND | FMOD.Studio.EVENT_CALLBACK_TYPE.DESTROY_PROGRAMMER_SOUND);

        // Convert our EventData to an IntPtr so it can be passed to our event instance
        GCHandle handle = GCHandle.Alloc(data);
        eventInst.setUserData(GCHandle.ToIntPtr(handle));

        // Start our instance
        eventInst.start();
    }

    [AOT.MonoPInvokeCallback(typeof(FMOD.Studio.EVENT_CALLBACK))]
    static FMOD.RESULT EventCallback(FMOD.Studio.EVENT_CALLBACK_TYPE type, IntPtr instancePtr, IntPtr parameterPtr)
    {
        FMOD.Studio.EventInstance instance = new FMOD.Studio.EventInstance(instancePtr);

        // Retrieve the user data
        IntPtr dataPtr;
        instance.getUserData(out dataPtr);

        // Get the data from our pointer
        GCHandle dataHandle = GCHandle.FromIntPtr(dataPtr);
        EventData data = dataHandle.Target as EventData;

        switch (type)
        {
            case FMOD.Studio.EVENT_CALLBACK_TYPE.CREATE_PROGRAMMER_SOUND:
            {
                FMOD.MODE soundMode = FMOD.MODE.LOOP_NORMAL | FMOD.MODE.CREATECOMPRESSEDSAMPLE | FMOD.MODE.NONBLOCKING;
                var parameter = (FMOD.Studio.PROGRAMMER_SOUND_PROPERTIES)Marshal.PtrToStructure(parameterPtr, typeof(FMOD.Studio.PROGRAMMER_SOUND_PROPERTIES));

                FMOD.Sound sound;
                // We will use the `CurrentProgInstrument` to retrieve the audio files paths from our list
                var soundResult = FMODUnity.RuntimeManager.CoreSystem.createSound(data.paths[data.CurrentProgInstrument], soundMode, out sound);
                if (soundResult == FMOD.RESULT.OK)
                {
                    parameter.sound = sound.handle;
                    parameter.subsoundIndex = -1;
                    Marshal.StructureToPtr(parameter, parameterPtr, false);
                }

                // Increment the index to use the next audio file path
                data.CurrentProgInstrument++;

                break;
            }
            case FMOD.Studio.EVENT_CALLBACK_TYPE.DESTROY_PROGRAMMER_SOUND:
            {
                var parameter = (FMOD.Studio.PROGRAMMER_SOUND_PROPERTIES)Marshal.PtrToStructure(parameterPtr, typeof(FMOD.Studio.PROGRAMMER_SOUND_PROPERTIES));
                var sound = new FMOD.Sound(parameter.sound);
                sound.release();

                break;
            }
            case FMOD.Studio.EVENT_CALLBACK_TYPE.DESTROYED:
            {
                // Now the event has been destroyed, unpin the string memory so it can be garbage collected
                dataHandle.Free();

                break;
            }
        }
        return FMOD.RESULT.OK;
    }
}

```

 ![image](https://canada1.discourse-cdn.com/flex036/uploads/fmod/original/2X/4/4c67c9431d781cb9241896f753b5d95ca5719416.png)

I haven’t implemented a way to set the parameter value but that is easily done with: [FMOD Engine | Studio Api Eventinstance - Studio::Eventinstance::Setparameterbyname](https://fmod.com/docs/2.03/api/studio-api-eventinstance.html#studio_eventinstance_setparameterbyname).

Please note, this script should only be used for testing.

Hope this helps!

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_[View the full topic](https://qa.fmod.com/t/support-hacky-user-assigned-music-through-programmer-instruments/23852)._