in these figures the cassette holder designated by 20 is arranged in a main body 22 of the tape recorder in such a manner that it is free to rotate about a hinged supporting point 20a also in fig1 on the left upper surface of the cassette holder 20 there is formed a window 24 for reading the amount of residual tape and on the right of the window there is provided a motor storage section 26 the above mentioned motor storage section 26 as shown in fig2 is a space present on the upper surface of the tape cassette 10 to be stored within the cassette holder 20 and also the motor storage section 26 is arranged such that it projects out into a space which does not interfere with the cover 10b of the cassette 10 when the cover 10b is opened or closed see fig3 and 4 in the motor storage section 26 there are arranged a motor 30 for switching modes a mode detection switch 32 a circuit substrate 34 with a drive circuit for the motor 30 on board the motor 30 has a drive shaft on which there are arranged a worm 36 and a pulley 38 the worm 36 is adapted to mesh with a worm wheel 32a and a timing belt 40 is wound round the pulley 40.