Override/Frequency Location Guide
HOW TO OBTAIN THE OVERRIDE FREQUENCIES FOR THE SLEEPER NODES
Too unlock these Sleeper Nodes - they're the same as the ones from the Arecibo Adventure on Io - you need to:
Complete the DLC main story and then complete the subsequent blue Ana missions on Mars to unlock the Nascent Dawn 1/5 Pursuit.
Complete 3 patrols and then complete a Lost Sector to acquire 4 Resonant Stems which you can combine into an Override Frequency for a specific music box to complete the Nascent 1/5 quest item.
The last 3 words of the Override Frequency item will give you a clue as to where the music box is located (and these key words are included in the list below).
Return to Ana and complete the new Diary 1/5 quest item by putting a thing you get from Ana into a thing near Ana to get a lore thing.
To obtain more Resonant Stems complete Patrols, Public Events (2 stems from Heroic PEs), Lost Sectors or loot the chests from high value targets - Ilheru Xolborne in the Glacial Drift, Yer'ot The Forgottenand a Cabal in the Braytech Futurescape.
I have found that the most efficient farming for Resonant stems is to continually complete patrol missions (they're all pretty quick except for the Psion collectable one) and complete Heroic Public events (2 stems each) and kill high level targets whenever they are available - make sure to complete the killing/gathering patrols during PEs and one of the traveling patrols when you are going for a Sleeper Node.
The rewards from each music box are random and usually include shaders and some sort of engram. I did get a "Braytech Schematic" from the 2nd one I opened (likely random) which can be turned in for a "Warmind Engram" which looks to be another type of Powerful Gear engram that can be used for the hard cap level grind.
With the First Sleeper Simulant acquired, it appears you don't need to complete all 40 of the Sleeper Nodes to unlock the gun, only 15 nodes need to be turned in as one of the steps on the IKELOS weapon quest. Now I wonder what completing all 40 will do, my guess is an ornament but we won't know until we know.
Just figured I'd put together a list of the cubes that require an override frequency for posterity once we can get those. Will continually update as new ones are added, feel free to help out.
The first picture is the location of your cursor/marker on the map, the second shows a picture of the surroundings. They are roughly in the order you would encounter them in those areas.
Descent.Cavern.Warsat - On a ledge just below the entrance to the PAVONIS 45 cache.
Descent.Chasm.Ledge - On a lower ledge on the south side of the large cave area by the Glacial Drift.
Descent.Caves.Runes - Just to the left of the entrance to the Penumbral Depths, which is blocked by a Hive door (initially, anyway).
Drift.Subterrane.Cliffside - On the left side just before you enter the Ma'adim Subterrane Lost Sector.
Drift.Transit.Freight - In a partially open container on the bridge.
Drift.Gatehouse.Catwalk. - In the building at the NW end of the bridge with the train tracks, up on the left catwalk behind the pillar. There is a region chest at the other end of the catwalk.
Drift.Transit.Foundation - Under the bridge on the NW end of the bridge.
Drift.Service.BackEnd - In the building on the way to the Braytech Futurescape, on the right side.
Drift.Checkpoint.Elevator - In the "C-67" Building on the SW end of the train track bridge, in the left room.
Drift.Flammable.Storage - In the left of the small building on the other side of the mountain from the SW end of the train tracks.
X.X.X. - Across from where you enter the Alton Dynamo in the wide open frozen area.
Drift.Subterrane.Chasm - In the Ma'adim Subterrane Lost Sector, under the thin bridge that leads the the 2nd area.
X.X.X. - In the Ma'adim Subterrane Lost Sector, after you cross the thin bridge to the 2nd area with Cabal.