What seems incoherent and unnecessary in "War jetzt morgen eigentlich Probe?" really isn't part of the question itself, but of a different communication level.
It has long since been stated by communication psychologists that human messages usually convey more that just one face value statement. Sender, recipient, and current circumstances are always part of a message. The German psychologist and communication expert Friedemann Schulz von Thun visualized this in his communication square model (Kommunikationsquadrat, later known as Vier-Ohren-Modell = Four-Ears model) *), where each message (questions are messages, too) consists of four components:
Sachinhalt (speaking of the matter itself)
Selbstkundgabe (speaking of the state and the sensitivities of the sender)
Beziehung des Senders zum Empfänger (how the senders rates his/her position in relation to the recipient's)
Appell (the sender appealing to the recipient, what the sender wants to get done by the recipient)
Not all messages put an equally strong strain on all levels, and sometimes, one or the other level may be "empty", but this is a generalising model providing a neat classification tool in the first place, and on the other hand, one cannot not communicate, as Paul Watzlawick put it.
It is obvious that we can't judge a message by means of this model without knowing anything about the speakers involved, their relationship, and the overall situation. But regarding the inconsistencies, we can at least try to analyse what additional meanings are hiding behind this question:
- The basic objective of the question is clear: the speaker wants to know if a rehearsal is scheduled for tomorrow. But why not simply ask:
Ist morgen Probe?
To answer this, we have to know the context. As we don't, we can't even decide upon this simple statement, as it could tell us different things about the situation and the persons involved. For example, the three hidden levels could be (to make things easier, let us assume the speaker = "S" is a man, the recipients = "R" are members of a brass band rehearsing for a local concert):
A2. S has just arrived from a business trip. It wasn't yet decided upon scheduling the rehearsal for tomorrow when he left.
A3. There was a consensus that S would be notified of the rehearsal date when he returned from his trip, contacting a member of R.
A4. S wants R to tell him when the rehearsal is.
B2. S has been told when the rehearsal will take place, but doesn't
remember because he is busy with other things or his memory is no
longer the way it used to be, but basically, he doesn't care,
B3. ..because he is well integrated in the group and R won't blame him
for asking twice for the information.
B4. S wants R to tell him when the rehearsal is.
C2. S hasn't been yet told about the upcoming rehearsal, he really
C3. The relationsship between S and R has become tense lately, there
have been differences, perhaps S is being mobbed by some members of R.
C4. S appeals to R to reconcile differences with R.
But let's go back to the original phrasing, "War jetzt morgen eigentlich Probe?". In your answers above, the words "jetzt" and "eigentlich" and the use of the preterite have been indicated as unnecessary or inappropriate.
The adverb jetzt used in a question often indicates impatience:
Kommst du jetzt endlich?
Was ist jetzt, entscheide dich!
Therefore, on the appeal level (4) of our question, jetzt could signify a demand of S towards R to make up their mind if there should be a rehearsal tomorrow. Accordingly, on level 2 and 3, it could mean that S wasn't involved in the decision making and wasn't happy about this.
But the effect of jetzt is very much mitigated by eigentlich which usually has an obliging connotation: basically it should be like this, but I am ready to make concessions for the sake of our good understanding. This would relate to level (3), making the intention of level (4) more optional, more like an invitation.
The use of the preterite instead of the present tense may be a statement of the second level. Without knowing the context and the persons involved, there are too many variables as to reasonably judge this component.
*) Friedemann Schulz von Thun: Miteinander reden 1, Störungen und Klärungen, Allgemeine Psychologie der Kommunikation. (rororo Sachbuch 17489) Reinbek bei Hamburg: Rowohlt Taschenbuch Verlag (46) 2008