what is difference between yaparken and yapıyorken?

more examples:

giderken vs gidiyorken

severken vs seviyorken

ağlarken vs ağlıyorken

No real difference. Tenses are flexible in Turkish. You can use one for another but of course not always

-rek  suffix which is a gerundium suffix, takes inflection suffixes [-ir, -iyor, miş,ecek ] unlike other gerundiums.

The aorist form of it [-erken ,-arkan,-irken, -ırken ] is used more commonly whereas the continuous form of it [-iyorken, ıyorken, uyorken, üyorken, -ecek ] is not that common.

Dün okula giderken yolda bir köpek gördüm.

I saw a dog while I was going to school.

Sen kahve yaparken telefonun çaldı.--->  While you were making coffee, your phone rang.

Sen kahve yapıyorken telefonun çaldı..---> This doesn´t sound very good to me.

Otobüsten inerken düştü.

Otobüsten  iniyorken düştü.

They both tell us same thing " He/She fell while [when] he/she was getting off the bus.

However, you will hear  people use the aorist form, generally. Since it sounds more natural.

You may hear people may use continous form in two parts of the compound sentence.

Şu an seni dinliyorken    aklımdan neler geçiyor biliyor musun ?

  1. part                               2. part

Now, as I am listening to you, do you know what is going through my mind ?

*Note : In the end , I would recommend you to stick with aorist form. [-erken ,-arkan,-irken, -ırken ] + ken

Thank you both, Tunci and Gokuyum  

The left column´s ones have been conjugated in simple present, the right column´s have been in present continuous. We usually prefer the present simple´s ones.

git+r(present simple)+iken(while)---------------->giderken

git+iyor(present continuous)+iken(while)--------->gidiyorken

Telefonum ben otobüse binerken düşmüş olmalı. (My phone must have fallen down while I was getting on the bus.)

telefon (telephone), otobüs (bus), binmek (to get on), düşmek (to fall down, to drop), olmak (to be)

Komşunun çocukları, bahçede oynarlarken çok gürültü yapıyorlar. (The children of the neighbour make big noise while they are playing in the garden.)

komşu (neighbour), çocuk (child), bahçe (garden), oynamak (to play), çok (1many, 2much, 3too), gürültü (noise), yapmak (to do, to make)

Deney yaparken çok dikkatli olmalıyız. (We must be very careful while we are experimenting.)

deney (experiment, proving), yapmak (to do, to make), dikkat (care), dikkatli (careful), -meli/-malı (must)

Kitap okurken müzik dinleme alışkanlığım yok. (I haven´t any habit of listening to music while I am reading book.)

kitap (book), okumak (to read), müzik (music), dinlemek (to listen), alışkanlık (habit), yok (there isn´t)

Teşekkürler Mehmet