A line with pop sense

Hum it first

tetsuya hears his melodies away from the instrument, humming, with the chord already felt under them. The instrument comes second.
His test for a guitar part he wrote: “What I play has to be simple, and yet stand out at the same time.” (tetsuya, Tetsugaku 04, translated)
Hum on “la”, not words: words stick and start steering the line.

The parts

Chord tones (root, third, fifth): strong beats. They tell the ear what the chord is.
Passing and approach tones: weak beats, a step away from the next chord tone. They make the line go somewhere.
The hook: one short figure that comes back, bent to fit each chord. Repetition is what makes it hummable.

Root on beat 1 still matters: the band hangs off it. The melody is what you do on beats 2 to 4.
A line moving between roots is the tetsuya sound; a line that never repeats is a solo. Keep the hook.

The same three parts write a good riff or second-guitar line. Play the loaner an octave up (the tab redraws on your low four strings), then try it in thirds on strings 3 and 2.

Shamisen has no chords to outline: the open strings (honchōshi C F C) are the strong notes. Put them on the beat and fill between with tsubo notes.
The hook is a short phrase that returns with a small change, the way min’yō accompaniment repeats its figure under each verse.

The loaner

A, F#m, D, E, one bar each, quarter notes. Each bar: root, root, up to the third, then a note one step from the next bar’s first note. The repeated shape is the hook.

Five or six strings: try bar 4 on the low E (open) instead of fret 2 on the D string for a bigger landing. Save the low B for when the song asks; tetsuya prefers a four-string’s evenness and tunes down for the rare low note.

Six strings: on the repeat, play bars 1 and 2 an octave up on the G and C strings as an answer, then drop back down.

Hear it

Do this

Play the loaner. Find the hook, a passing tone, and a chord tone on beat 1.
Instrument down. Over the same four chords, hum your own line on “la” until it repeats the same way twice.
Find it on the neck. Chord tones on the strong beats.
Beat 4: change it to a note one step from the next bar’s first note.
Pick one figure and make it come back each bar, bent to the chord.
The hook test: play it for a minute, put the instrument down, hum it. Can’t? Simplify.
Tab it and send it to your tutor, then log the session:

Check

Every beat 1 is a chord tone
Every beat 4 leads somewhere
You can hum it an hour later