Once discovered, all of the below effects can be toggled on/off in the "+" menu.

Snow Globe
Key/Notes: bbbbbcb
Actual Tune: Winter Wonderland
Effect: Creates a halo of snowfall encompassing your mountain.

Blood
Key/Notes: mmmmmm,mnab
Actual Tune: Moonlight Sonata (Beethoven)
Effect: Rains blood. I'm not sure why the Moonlight Sonata inspires this?

Fish
Key/Notes: cxzxcccxxxcbb
Actual Tune: Mary Had a Little Lamb
Effect: Rains fish.

Frogs
Key/Notes: bbaassa,,mmnnb
Actual Tune: Twinkle Twinkle Little Star
Effect: Rains frogs.

Hearts
Key/Notes: ssfssfsfjhggf
Actual Tune: Lullaby (Brahms)
Effect: Rains hearts.

Flames
Key/Notes: cvbnmbm
Actual Tune: In the Hall of the Mountain King (Greig)
Effect: Meteor shower.

Coins
Key/Notes: cccccccbzxc
Actual Tune: Jingle Bells
Effect: Rains coins.

Artefacts
Key/Notes: vmvmamamadadadgnanad
Actual Tune: Ride of the Valkyries (Wagner)
Effect: Increases the frequency of artefacts appearing.

WARNING: Too many artefacts falling on your mountain will destroy your trees. At this point, I'm not sure if the trees will grow back or if there is a way to regrow them once they are gone.

UPDATE: I've recieved a tip from user 'Aande' that trees CAN regenerate if you spam notes to speed up the time. The tree count can be viewed in the stats menu. I have not yet verified this personally but wanted to add it here for everyone. I'll update again once I get a chance to check.

Thoughts
Key/Notes: m,kj
Actual Tune: ??? (I don't think this is actually a tune)
Effect: Prompts your mountain to share a thought on demand. Alternatively, the "." key also works as a shortcut.

Clear Artefacts
Key/Notes: sss,aaam
Actual Tune: Symphony No.5 (Beethoven)
Effect: Clears all artefacts from your mountain.

Annihilation
Key/Notes: as,zb
Actual Tune: Close Encounters of the Third Kind
Effect: This will prompt a dramatic scene where a large object (randomly generated) will crash into your mountain and destroy it, causing your game to reset.

NOTE: Mashing the key/notes frantically will generate a field around your mountain which can save it and spare you from having to restart at the beginning.

Extra Key/Notes
Key/Notes: asa,mnbvcvv
Actual Tune: The Sound of Music
Effect: Unlocks additional key/notes, extending the high range. Keys "Q - I" are added.

Stats Menu
Key/Notes: fs,n,sfs,n,s,
Actual Tune: La Fille aux Cheveau (Debussy)
Effect: Unlocks a secret menu that displays your mountain's stats and allows you to load from a previous save. Once activated, this menu can be accessed via the new "square" icon.

WARNING: The "Regen" option resets your mountain and starts you at the very beginning. It is essentially the same as 'Annihilation' except without the dramatic destruction sequence.

This section contains some general tips, tricks, and insights for managing your mountain.

Moving Artefacts:
To rearrange the items on your mountain, simply click and hold your left mouse button on the object (you will hear a rumbling sound) which will pluck it off of your mountain and allow you to recast it towards a different location.

Discarding Artefacts:
To send an unwanted object back into space, you'll need to first pluck it off of your mountain then cast it towards space. This can be tricky as you'll need to aim the object in such a way as to completely miss your mountain since you can't throw away from the surface. I found the best way to do this is to aim at the very bottom tip on the underside of the mountain. Eventually the object will miss the mountain and keep going past it.

Avoiding Artefacts:
Spamming the keys at the right time (in the same way as causing the 'Acceleration' effect described below, will allow you to avoid any undesired incoming artefacts from landing on your mountain. The temporary halo created acts as a barrier but this will only work if the artefact has not yet entered the atmosphere. (Thanks to another player 'Nino' for this tip).

Acceleration:
Button-mashing the key/notes will increase the rotation of your mountain and speed up the passing of time. This also creates a temporary halo around your mountain which can be seen if you zoom out.

Gust of Wind:
Hold the left mouse button and shake the cursor to clear away the clouds. This will also affect any current rain effects.

Toggle Screen Size:
You can use keys 1-4 as a shortcut to toggle the screen size without having to activate the menu options.

Artefacts that Like to Crash with Style:
These objects have special animations when cast.

• Blue Astroid: on fire
  
• Red Astroid: on fire
  
• Heart: heart trail + small explosion of hearts upon landing
  
• Plane: on fire
  
• Biplane: on fire
  
• Dice: crashes with bubbles (contributed by 'Bridget (maybe Dale don't ask)')

Artefacts that Light Up:
These objects emit their own light on the mountain.

• Blue Astroid
  
• Red Astroid
  
• Light Bulb
  
• Lamp Post

Interactive Artefacts:
You can interact with these objects on your mountain. So far, I only know of one...

• Gramophone: Click on this object and it will play one of three Albert Bowlly songs.
  
  • Night and Day
    
  • All I Do is Dream of You
    
  • Dreaming

Just for fun I thought I would add a section here on the many ways your mountain can be destroyed. Below are the possible messages you can get after activating the Annihilation sequence.

The below entries are the ones I have personally verified within my own game:

• You have been destroyed by The Eye Of Love Unrequited
  
• You have been granted death by The Sun Of Infinite Darkness
  
• You were destroyed by A Giant Cube From Hell
  
• You were killed by The Murderous Dwarf Star
  
• You were killed by a XYZZYX
  
• You were destroyed by The Icosahedron Of Doom

Here are some other ones I've seen / contributed by others:

• You are granted death by The Eye of Annihilation
  
• You died by The Arrow of Infinite Pain and Sorrow
  
• You have been killed by The Eye Of Blindness
  
• The Taker Of Souls Took Yours
  
• The Taker Of Life has Taken Yours (contributed by 'PwnCakes')
  
• You were killed by a passing sun
  
• You are ruined by a passing Giant Sun
  
• You have been granted death by the sun of infinite darkness (contributed by 'Lorvanus')
  
• You were annihilated by a Giant XYZZYX
  
• A tiny XYZZYX killed you
  
• You have been killed by a Giant Ice Cream
  
• You were killed by the Blood Pyramid
  
• You were killed by Rupert, The Bringer Of Ice
  
• You were killed by Fluffy, The Bringer Of Guilt
  
• You where killed by Rupert, Keeper of Life (contributed by 'arbadar')