grammar - Grammatical name of the form used before -て, -たり, -た, -た ら?

I'm looking for the Japanese name of the specific verbal form used before -て, -たり, -た, -たら:

verb      → 連用形 ren.yōkei → XXXX    →   + -て, -たり, -た, -たら

書く      → 書き             →  書い   →   書いて, 書いたり, 書いた, 書いたら

I assume this verbal form is derived from the 連用形{れんようけい}, with specific phonetic modifications for godan verbs. (see Shimamori Reiko, Grammaire japonaise systématique.1.48 (my translation): "-て, -たり, -た, -たら are preceded by the connective base of the verb, [...] yodan verbs [...] being deeply modified [by the suffix]")

So, what's the name standing for "XXXX"? Something like "-t" form?

Answer

They are also treated as 連用形. More specifically i-type are called 連用形のイ音便. Sometimes 音便形 is used, but there are no official name.

References

1. 音便形 in デジタル大辞泉


2. 動詞の音便（おんびん） イ音便・撥音便（はつおんびん）・促音便（そくおんびん）



3. 音便 - Wikipedia (Note: This article uses 動詞のテ・タ形 for conveniece sake.)