In Ecclesiastical Latin, certain letters are used together to create a sound that one letter by itself is not able to make. An example of this in English is when we put an H after an S to create the SH sound as in Shopping. Latin does a similar thing, but instead of an H, we use a C. However, SC will not change in all places. As we saw with C and G before A,O,U, when they did not change, so SC does not change sound before these letters. Before the AOU letters, SC will sound like the SK in the English word Skip.
However, before E,I,Y; just as C and G changed sound, so SC will change from an SK sound to the SH sound.
So SCOPO will sound as SKOPO. However SCINDO will sound as SHEENDO.
This rule is simple to learn as all you need to is keep in mind that AOU and EIY are two different groups of vowels and C,G, and SC that go with them will change sound. This rule also has implications when pronouncing certain words.
If there is an X followed by a C then which is then followed by EIY, then an interesting thing will happen. The X will loose its sound of KS and will blend with the C. If we break the X apart this is what we are really saying;
This will sound not as KS CHEH but rather as K SHEH as in the capital letters in the following words. neCK SHEll. An example of when this happens is in the word EXCELSIS from the Gloria. eKSHEllsees
The next combination we will look at is the GN combination. It often sounded as the NY in the English word caNYon. On very rare occasions, some people who have studied too much Greek will misspell this as GG in imitation of the Greek. Please don't do this.
The next issue is not so much a blend that happens on purpose to create a sound not represented in the Alphabet but rather is a sound that happens by accident as a result of how people just naturally pronounce the words. Since this is a naturally occurring case, the rules for when it happens and when it does not may seem odd at first.
If the letters TI do not have an S before them and are followed by at least one more vowel then a slight s sound will happen between the T and the I. Also, this does not happen if the TI begins the word. So;
begins the word
Tiara - Tee Ahrah just as written
preceded by S
Constituere - KonSTEEtoo ehre just as written
not followed by at least one more vowel sound
Continens - KonTEEnens just as written
Continentia - konteenenTSEEa not exactly as written when pronounced naturally
Most words that do this will be have it at the end and will end in things like tia or tio. In English we have some of these as in action. However, unlike English which changes the TI to a SH sound, in Latin just add a slight Ssound after the T. Some writers will misspell this as Z, but you should avoid this practice as Z is reserved for words of Greek origin that have not been fully Latinized.
The last bit to mention here are the vowel blends. Most of the time, in a Latin word, all vowels will be pronounced distinct and separate from each other. On rare occasions UI may be allowed to sound like English WEE but this is avoided. More often we will allow the U to turn into a V sound to give us VEE.
EU in many borrowed words will sometimes sound as JU but again, this is avoided and if you don't do it, you will be alright.
There are some vowel blends that are not avoided but in fact encouraged.
AU will sound like the OU in the English word OUT. This natural.
AE and OE will often just sound like E, the open sounds before it being drowned out. Some speakers will pronounce these as an E with just a slight I sound after but you don't have to do this.
Besides these, all vowels are to be pronounced distinct and separate from each other.