Learn Hardcore Swahili: Wakati nilikuwa nikifanya mazoezi ya viungo jana, nilisikia muziki mzuri kutoka kwa jirani. - While I was doing physical exercises yesterday, I heard nice music from the neighbor.

So nilikuwa nikifanya mazoezi ya viungo jana = “I was doing physical exercises yesterday”, emphasizing that the action was ongoing at that time.

If you said:

nilifanya mazoezi ya viungo jana
→ “I did physical exercises yesterday” (simple past, whole event as a completed fact)

In this sentence we want the exercises as background to something else (hearing the music), so Swahili uses the past continuous: nilikuwa nikifanya.

Why is the first action (nilikuwa nikifanya) continuous, and the second one (nilisikia) simple past?

This is the same contrast English uses in sentences like:

“While I was doing exercises, I heard some nice music.”

In Swahili:

nilikuwa nikifanya mazoezi ya viungo jana
→ background, ongoing action (I was in the middle of exercising)
nilisikia muziki mzuri
→ main event, a single occurrence (I heard music once / at that moment)

So:

Continuous (nilikuwa nikifanya) = what was already happening
Simple past (nilisikia) = what happened during that time, as a specific event

Swahili marks this contrast almost exactly the way English does in this kind of story-telling.

What exactly does wakati do here? Does it mean “when” or “while”?

Wakati is a noun meaning “time”, but very often it works like the conjunction “when / while”.

In this sentence:

Wakati nilikuwa nikifanya mazoezi ya viungo jana, nilisikia muziki mzuri... → “While I was doing physical exercises yesterday, I heard nice music...”
or “When I was doing...”

So:

wakati + clause = “when/while (something happens/happened)”

You can also treat wakati more literally as “the time (that)…”:

Wakati nilikuwa nikifanya mazoezi...
→ “At the time (when) I was doing exercises...”

Both “when” and “while” are natural translations here; the Swahili doesn’t strictly force one over the other.

Can I use nilipokuwa instead of wakati nilikuwa?

Yes, that’s a very common alternative.

Wakati nilikuwa nikifanya mazoezi ya viungo jana, nilisikia muziki mzuri...
Nilipokuwa nikifanya mazoezi ya viungo jana, nilisikia muziki mzuri...

Both mean roughly:

“When I was doing physical exercises yesterday, I heard nice music...”

Differences:

wakati explicitly mentions “time”.
nilipokuwa = ni- (I) + -li- (past) + -po- (when/where) + kuwa (be).
Literally: “when I was”.

Stylistically:

nilipokuwa... often feels a bit more compact and very natural in narratives.
wakati nilikuwa... is also fully correct and common.

So you can safely use either in this context.

Why is it nikifanya after nilikuwa? Could it also be nilikuwa nafanya?

Both forms are possible and common:

nilikuwa nikifanya mazoezi...
nilikuwa nafanya mazoezi...

They both often translate as “I was doing exercises”. The difference is subtle:

ni-ki-fanya
- -ki- here marks an action in progress / ongoing, and is also used in “while doing” clauses (nikifanya = while I’m doing / as I do).
- nilikuwa nikifanya combines kuwa
  - this -ki- form for a strong sense of ongoing activity.
na-fanya
- -na- is the usual present tense marker.
- With nilikuwa, nilikuwa nafanya functions like a past continuous: “I was doing / I used to do”.

In everyday speech, you’ll hear both. Many speakers use nilikuwa nafanya more often; nilikuwa nikifanya can sound a bit more “story-like” or explicitly progressive. In this sentence, either would fit.

What does mazoezi ya viungo literally mean, and is it the normal way to say “physical exercise / workout”?

Literal meanings:

zoezi = an exercise (singular)
mazoezi = exercises, practice, training (plural, but can be used as a mass noun)
kiungo / viungo = joint(s), limb(s), body part(s)
mazoezi ya viungo = “exercises of (the) limbs/joints”, i.e. physical exercises.

Yes, mazoezi ya viungo is a natural and common way to say:

physical exercises
gymnastics / workout-type exercises

You might also see/hear:

mazoezi ya mwili – body exercises, physical exercises
kufanya mazoezi – to exercise / to work out (no need to specify ya viungo if context is clear)

In this sentence, mazoezi ya viungo nicely matches “physical exercises” or “working out” in English.

Why is it mazoezi ya viungo and not mazoezi la viungo or mazoezi za viungo?

The small word (ya / la / za / etc.) must agree with the noun before it in noun class and number. Here:

mazoezi is class 6 (ma-).
The linker (of) for class 6 is ya.
viungo is class 8 (vi-), but the linker agrees with mazoezi, not viungo.

So:

mazoezi ya viungo = exercises of (the) limbs/body parts

If the head noun were different, the linker would change:

zoezi la mwili (class 5) = an exercise of the body
vitabu vya watoto (class 8) = children’s books
siku za kazi (class 10) = working days

In short:

ya is correct because it matches mazoezi (class 6).

Why is it muziki mzuri and not mzuri muziki?

In Swahili, adjectives normally come after the noun they describe:

muziki mzuri = good / nice music
mtu mzuri = a good person
kitabu kizuri = a good book

So:

muziki = music
mzuri = good, nice, beautiful (adjective)

Putting the adjective first (mzuri muziki) is not correct standard Swahili. The normal pattern is: > [noun] + [adjective]

Also note that mzuri agrees with muziki’s noun class (class 3). For the plural (if you were talking about several types of music), you’d have:

mimuziki mizuri – good kinds of music (much rarer in everyday use, but grammatically the pattern is there: mu- → plural mi-, mzuri → mizuri).

What is the role of kwa in kutoka kwa jirani? Why not just kutoka jirani?

Kutoka means “from”, but Swahili often distinguishes between:

from a place → usually kutoka + place
- kutoka nyumbani – from home
- kutoka sokoni – from the market
- kutoka shuleni – from school
from a person (or their house, or their direction) → usually kutoka kwa + person
- kutoka kwa jirani – from (the) neighbor / from the neighbor’s (place)
- kutoka kwa mama – from mum
- kutoka kwa rafiki yangu – from my friend

In kutoka kwa jirani:

It suggests the source of the music is associated with the neighbor (their house / their place).
Literally, you can think: “(coming) from at the neighbor”.

You might hear kutoka jirani in some casual speech or influenced by local patterns, but the standard, clear form for a person is kutoka kwa jirani.

How would I say “from my neighbor” or “from the neighbor’s house” more explicitly?

You can add a possessive after jirani:

kutoka kwa jirani yangu
→ “from my neighbor”

If you want to be very explicit about the house/place:

kutoka kwa jirani yangu already usually implies “from my neighbor’s place/house” in context.
Or you could say:
- kutoka nyumbani kwa jirani yangu
  → “from my neighbor’s home/house”

Pattern:

[preposition] + [jirani] + [possessive]
- kwa jirani yangu – at my neighbor’s / from my neighbor
- kwa jirani wake – at/from his/her neighbor
- kwa majirani – at/from the neighbors

Why is jana (yesterday) placed before the comma, inside the first clause? Could it go elsewhere?

Yes, jana is flexible in position. In the sentence:

Wakati nilikuwa nikifanya mazoezi ya viungo jana, nilisikia muziki mzuri...

jana belongs to the action of doing exercises. You could also say:

Jana nilipokuwa nikifanya mazoezi ya viungo, nilisikia muziki mzuri kutoka kwa jirani.
Nilipokuwa nikifanya mazoezi ya viungo jana, nilisikia muziki mzuri kutoka kwa jirani.
Nilisikia muziki mzuri kutoka kwa jirani jana nilipokuwa nikifanya mazoezi ya viungo.

All are grammatically possible. The most natural options usually put jana:

near the verb whose time it modifies (nilikuwa nikifanya), or
at the very beginning as a general time frame (Jana, ...).

The original sentence is fully natural: jana clearly refers to when the exercises (and the hearing) happened.

Could I drop wakati and just say Nilikuwa nikifanya mazoezi ya viungo jana, nilisikia muziki mzuri…?

You can drop wakati, but the sentence then feels less clearly like a “while X, Y happened” structure and more like two statements side by side.

Compare:

Wakati nilikuwa nikifanya mazoezi ya viungo jana, nilisikia muziki mzuri kutoka kwa jirani.
→ Strong, explicit “While I was doing exercises yesterday, I heard nice music from the neighbor.”
Nilikuwa nikifanya mazoezi ya viungo jana, nilisikia muziki mzuri kutoka kwa jirani.
→ Grammatically okay, but feels like:
“I was doing exercises yesterday, I heard nice music from the neighbor.”
The link “while” is more implied than stated.

A very natural way to express the same idea without wakati is to use nilipokuwa:

Nilipokuwa nikifanya mazoezi ya viungo jana, nilisikia muziki mzuri kutoka kwa jirani.

So yes, you can drop wakati, but it slightly weakens the explicit “while” connection unless you replace it with nilipokuwa.