Finale is one of the best MIDI composition software for Macintosh. It incorporates everything an author needs to compose music with their Mac.
This version was optimized for PPC.
You'll have to enter a serial number as follows: "MFNA-" followed by the 6 figures of your serial
number.
TIP if you can't hear MIDI playback:
This is from someone who was trying this on a iBook G3 clamshell Mac OS 9.2 but there was no sound:
With Finale 3.7.2 running, go to Options > Midi Setup...
From there, you need to select Open Music System, and for Output Device, QuickTime Music. If you can't see Open Music System, then it's not installed, and you'll need to get it. I can't remember if it comes with this version of Finale, but the installer is at least found from Finale Allegro 2002 install disk. In jargon, it's often referred to as 'OMS'.
Then, if the playback controls aren't visible, make them visible from the Window menu. In the Playback Controls window, click "More choices". Next, put a check to the box "Internal Speaker Playback". This is slightly misleading: On my iBook, the MIDI sound will be audible either from the computer's internal speaker (logical) or if I have speakers or headphones plugged in to the output port, the sound will come from them (counterintuitive, when you might expect "internal speaker playback" to strictly refer to the computer's own built-in speaker only).
(2.95 MiB / 3.1 MB)
Finale v3.7.2 / compressed w/ Stuffit

135 /

2017-03-25 /

7827aaec4bc6bfa5ad42d673ff81cddf6f622450 /

/
(5.34 MiB / 5.6 MB)
Version 3.7 and update 3.7.2 / compressed w/ Stuffit

92 /

2017-04-03 /

5d012634b22a959841683a169e188daec1daeabd /

/
Architecture 

68K + PPC (FAT)
System Requirements 
From Mac OS 7.5
up to Mac OS 9.2
Compatibility notes 
Architecture: 68K + PPC (FAT)
At least 4.5MB of free RAM (may require more, depending on your project complexity)
Mac OS 7.5 - Mac OS 9.2.2
Can be installed and run in Mini vMac in spite of the virtual memory limits.
Emulating this? It could probably run under:
SheepShaver