I dithered about posting this or sending it a s private message
However, I think that it will underscore and reinforce some things for others, so in the spirit of teaching all, herewith my comments, corrections and suggestions:
Counterpoint exercises
Species 1
Your original line...
[mp3]http://www.bandcoach.org/fp/audio/sh-cf-cp-01.mp3[/mp3]
Parallel unisons are not independent. The point of all counterpoint is to create independent lines within the same harmonic framework
My corrected line...
[mp3]http://www.bandcoach.org/fp/audio/sh-cf-cp-02.mp3[/mp3]
Species 2
Your original line...
[mp3]http://www.bandcoach.org/fp/audio/sh-cf-cp-03.mp3[/mp3]
In all species of counterpoint a parallel 8ve or 5th or movement from 5ths to 8ves and vice versa may not occur in any of the notes in the CP against any two consecutive notes of the cantus firmus.
In your example above the 5th to Unison in bar 1, 5th to 8ve in bar 2 are all examples of this parallel movement.
Your direct parallel movement of 8ve to 8ve in the last two notes is permitted in all species of CP, though it is preferable to approach such by contrary motion rather than similar motion.
My corrected line...
[mp3]http://www.bandcoach.org/fp/audio/sh-cf-cp-04.mp3[/mp3]
Species 3
Your original line...
[mp3]http://www.bandcoach.org/fp/audio/sh-cf-cp-05.mp3[/mp3]
The final note should sound at the same time as the cantus firmus, not be anticipated; even though this is a dissonance that resolves to a consonance (7th to 8ve), it is not resolved effectively. The stricture from Species 1 as to the last note of the CP being the 7th of the scale still stands
Parallel 8ves and 5ths occur in bar 2 (8ve to 5th) and, bar 3 (5th to 8ve).
My corrected line...
[mp3]http://www.bandcoach.org/fp/audio/sh-cf-cp-06.mp3[/mp3]
There is a contrary motion between the 5th above the D in bar 3 to the 8ve C’s in bar 4 - this is permitted.
Species 4
Your original line...
[mp3]http://www.bandcoach.org/fp/audio/sh-cf-cp-07.mp3[/mp3]
The unison in bar 3 lessens the sense of independent lines, as noted in species 1.
You may only break the Species by reverting to Species 2 rhythm (2 against 1) so you may have had a possible alternative as the following
[mp3]http://www.bandcoach.org/fp/audio/sh-cf-cp-08.mp3[/mp3]
though you would have been better to do this instead
[mp3]http://www.bandcoach.org/fp/audio/sh-cf-cp-09.mp3[/mp3]
Altering the cantus firmus to remove problems is never an option when working counterpoint exercises.
If we were to correct the other deficiencies in the last minor correction, we might get something like this (not that CF has been restored to its original state):
[mp3]http://www.bandcoach.org/fp/audio/sh-cf-cp-11.mp3[/mp3]
My corrected line...
[mp3]http://www.bandcoach.org/fp/audio/sh-cf-cp-10.mp3[/mp3]
The direct parallel movement of 8ve to 8ve in the last two notes of the cantus firmus is permitted in all species of CP, though it is preferable to approach such by contrary motion rather than similar motion.