What kind of Russian orthography is this?

Question

This is a screenshot from Tchaikovsky's Harmony textbook:
(from page 5 of an 1897 edition — link to PDF)

And here is a transcription:

Ученіе объ интерваллахъ.

Хотя предполагается, что приступающій къ изученію искусства музыкальнаго сочиненія, достаточно подготовленъ къ тому обстоятельнымъ знаніемъ элементарнаго отдѣла музыкальной науки, мы считаемъ, однако же, не безполезнымъ предпослать нашему руководству краткое изложеніе ученія объ интерваллахъ, такъ какъ шаткія объ этомъ предметѣ свѣдѣнія могутъ препятствовать успѣшному изученію гармоніи.

Подъ интервалломъ разумѣется отношеніе, образуемое между двумя звуками по высотѣ. Въ каждомъ интерваллѣ звукъ, лежащій ниже, называется основнымъ. Наименованія интервалловъ соотвѣтствуютъ латинскому обозначенію отношенія, образуемаго между верхнимъ звукомъ и основнымъ.

Is this the pre-reform orthography? If someone is learning modern Russian, how difficult will it be to understand such paragraphs?

Answer 1

Yes, it's the Russian pre-reform orthography. The reform took place in 1918, so this is just hundred-year-old Russian. It's easy to understand — just like it's easy to understand hundred-year-old English. The main difference from Modern Russian is that it uses some letters that were removed from the alphabet in 1918 and were replaced by different letters.

In order to convert a text like this into Modern Russian orthography, perform these steps:

1. Remove every ъ, "hard sign", at the end of words, e.g. объ → об

2. Replace the obsolete letters with modern ones:

   ѣ → е, e.g. разумѣется → разумеется

   i and ѵ → и, e.g. ученіе → учение

   ѳ → ф, e.g. Ѳедор → Федор

   Note: Your sample passage has no ѵ or ѳ, but these were also used, albeit rarely.

3. Substitute the adjective endings:

   -аго → -ого, e.g. образуемаго → образуемого

   -яго → -его, e.g. синяго → синего

   -ыя, -ія → -ые, -ие, e.g. шаткія → шаткие. This also applies to the pronoun ея → её, but this word isn't in your sample.

4. Replace з with с on the ends of the prefixes before voiceless consonants: безполезнымъ → бесполезным

That's all. You'll end up with Modern Russian orthography, modulo spaces and punctuation in some edge cases.

To make it even simpler, there's an online converter, which can convert whole passages to and from the two orthographies.