Let me again restate by desired volume adjustment, working in SONG mode with sequencer data, I have my part volume for track 7 (before any control messages) set to 85 to start the song. I want it to continue at this same volume level for measures 1-89. I then want to raise my Track 7 volume to 125 at measure 90 and remain at 125 to the end. What is the correct control message event(s) and value(s) that I should insert? I tried just one CC 07 - 125 at measure 90, but it raised the volume from the beginning. Why? There are no other Control Change events and my track volume was set to 85. What happened / what did I miss do wrong?

The last sent MIDI CC message persists.
Like one the Newtonian Law of Physics that states an object at rest will tend to stay at rest until a force acts on it.

Your Track Volume setting CC = 85 is the setting for Track Volume on the Mixer — it is the Volume setting Stored in the Mixing setup associated with this Song. It will remain set at 85 until a CC7 event tells it to do something different.
At the top of measure 90 on Track 7 you “Insert” a “Control Change” Event CC7 = 125.
The Volume of the Part in slot 7 is set to 125, and there it will remain until you change it.

Question is: what will cause it to change?

There are three methods to change it.
1) Recall the Song — you would do so by moving away and then completely recalling the Song. The act of actually recalling the Song re-sends all the Mix settings; resetting everything to the initial condition of the Tone Generator, as originally stored (Part 7 was stored at 85). Simply returning to measure 1 does not recall the initial MIX settings. Only moving away and then manually Recalling the Song does. It does this by sending a reset all controllers message, and reading the stored settings. (This is only an issue if you want to rePlay the Song immediately … on stage, you’d probably move to the next Song, recalling its stored settings.
2) place an Event CC7 = 85 at the very top of the Song on Track 7, measure 001-01:000 cc7 = 85 (guarantees returning to the top will reset that volume.
3) place the initial mix setting in Scene 1. Here’s how: Recall the Song, make sure everything is in the proper “Start Condition”, (Track 7 should be at Volume 85) press [STORE] + [SF1] to Store the start condition in Scene 1. When the Song is over- if you immediately want to play it again, press [SF1] to reset your mixer to start condition. This will return track 7 volume to 85. This avoids having to move away and back to the Song in question.

From now on, you must be aware of your “start condition” Mix values. Storing Scene memory is adding a type of Automation. Changing values in the mix at certain measures along a linear timeline… means you must stay aware of the most recent command sent. Remember it persists… and will remain where it was left last. Imagine you fade out a track… fade it complete to 0. There it will stay until you reset the mix by completely recalling the Song, or by sending it a Scene automation command to immediately reset to the ‘start condition’.

Extra Credit: Using the Sequencer like a Boss
Because MIDI data “persists” - how can we guarantee the mix integrity is we don’t start playback from the very start?

From SONG Mode, Go to [UTILITY] > [F3] SEQ > [SF3] OTHER
SongEventChase — Event Chase allows you to specify which non-note data types are properly recognized during fast-forward and rewind operations. Normally, if a Song or Pattern is played back from mid-point and/or fast-forward or rewind are used, certain data types (such as Program Change, Pitch Bend, and Control Change) may not play back as expected. Setting this to a specific event ensures the playback integrity of the event, even when fast forwarding or rewinding.

Settings: Off, PC (Program Change), PC+PB+Ctrl (Program Change+Pitch Bend+Control Change), all (All events)
note — Keep in mind that settings other than “off” may result in slower operation — for example, a pause before starting playback, or slower rewind/fast forward speed.
note — When this is set to “all,” an excessive amount of MIDI data may be generated, possibly resulting in a MIDI error on the connected device.

What this means is if you fast forward from the beginning to measure 105… even though Track 7 was initially Volume = 85… if you now start from measure 105, the Event Chase set to “look up” the most recent changes to CC and will find that the last given CC7 message was 125 and it will recall the most recent value for all your CC messages…when you hit Play the volume will already be 125…smart!

Thank you Phil.... Extra, Extra Credit ??? Instead of Event Chase, couldn't I also simply create a second Scene with the increased level, then use SF1 and SF2 to set the correct levels depending on whether my replay point is before or after the measure I changed the levels?

Use of Scenes was one of the options.

3) place the initial mix setting in Scene 1. Here’s how: Recall the Song, make sure everything is in the proper “Start Condition”, (Track 7 should be at Volume 85) press [STORE] + [SF1] to Store the start condition in Scene 1. When the Song is over- if you immediately want to play it again, press [SF1] to reset your mixer to start condition. This will return track 7 volume to 85. This avoids having to move away and back to the Song in question.