Tak

Tak (also known as TAK) is an assistant producer for Fishmans known for his work alongside the band's primary producer, ZAK. Incredibly little is known about them, aside from them being some kind of audio engineer working at Polydor. In the CD Extra Dictionary's entry regarding Tak, he is claimed to be ZAK's apprentice, as well as providing some context as to his involvement with the group.

Untranslated Japanese Dictionary Entry
タック【ＴＡＫ】（人） 1) スペシャル・スーパー・エンジニア、ＺＡＫの弟子。そのテクニックは一子相伝…のわけがないか。

English Auto-translated Using DeepL Translate
TAK [TAK] (Person) 1) Special Super Engineer, ZAK's apprentice. His techniques are passed down from one generation to the next...how can that be?

This entry suggests that Tak may be significantly younger than ZAK, though beyond this very little is known about the assistant engineer. He is credited as having worked with the group since late 1995/early 1996 with 空中キャンプ, and up until mid 1998 with 8月の現状, which would have meant Tak's involvement had lasted significantly later than ZAK's involvement with the band, having left in mid 1997.