Blender 2.9 + Python script – Need help adding multiple action clips / action strips to an NLA track

Question

How can you add multiple action clips to a single NLA track in Blender 2.9 using a Python script?

I'm trying to loop through a file with rows of:

frame_number=X, object_name=Y, animation=Z

e.g.

frame_number=1235, object_name=31, animation=action_off

I'd like to loop through these rows and do the following:

Select the object_name at the frame_number

Select PianoKeyAnimations NLATrack.

If action_on add KeyPress animation. If action_off add KeyRelease animation.

Deselect PianoKeyAnimation NLATrack, KeyPress / KeyRelease animations and object_name in the Scene Collection.

The NLA action clips/strips I've set up are:

- KeyPress: Duration of 1 frame
- KeyRelease: Duration 1 frame

Here's the portion of the script that I'm struggling with:

# Select Nlatrack based on name
def nlaselect(trackName):
    ob = C.object
    ad = ob.animation_data
    if ad:
        for i, track in enumerate(ad.nla_tracks):
            # Find NLA track 
            track.select = track.name.startswith(trackName)
            # make active track if in pos 0
            if track.select and not i:
                ad.nla_tracks.active = track

all_tracks = {DATA_HERE}

current_area = bpy.context.area.ui_type
bpy.context.area.ui_type = 'NLA_EDITOR'
current_frame = 0
frames_delay = 240 # Delay animation by 4 seconds in 60 fps render

for row in all_tracks:

    current_frame += row.frame_number

    C.view_layer.objects.active = 
    D.collections['INSTRUMENT'].all_objects[str(row.object)]
    C.object.select_set(True)
    bpy.context.area.ui_type = 'NLA_EDITOR'
    C.object.animation_data.nla_tracks.active = None
    C.scene.frame_set( current_frame + frames_delay )
    
    if row.animation == 'action_on':

        nlaselect('PianoKeyAnimations')
        bpy.ops.nla.actionclip_add(action='KeyPress')
            
    if row.animation == 'action_off':

        nlaselect('PianoKeyAnimations')
        bpy.ops.nla.actionclip_add(action='KeyRelease')
            
bpy.context.area.ui_type = current_area
C.object.select_set(False)

This seems to be creating multiple NLATracks with the selected objects.

See screenshots: