Unexplained volume change

[Tim Mariott]

Sherry

The attached piece has been created from a MIDI file created by a choir colleague using another (much inferior!) software product: it just helps me to share out the load of keying in choir pieces.

The process normally works fine but in this piece I have some unexplained and disconcerting volume changes as follows -

1. Measures 85 to 87: Soprano stave increases volume
2. Measure 87: Alto stave increases volume
3. Measures 135-147: Baritone and Bass staves increase volume.

I normally have the volume set to a constant value for choir pieces, so it is a bit offputting when a part suddenly increases volume without any warning.

I cannot see anything to indicate a volume change and I have tried resetting the volume for the misbehaving measures - but with no luck.

Can you suggest any other remedial actions please. Many thanks.
Tim