+ Windows9Professional
The hand schematic below is the best I could do given the components (just one PNP transistor would have allowed a better and simpler circuit).
I haven't analyzed the circuit in detail, but it should give you something to experiment with.
The multivibrator, Q1 and Q2, does exceed the -VBE limit of the BC337 (-5V max), but the base reverse current would be limited so the multivibrator should work OK.
The output will be approximately 3V RMS, at around 70Hz, and the waveform will be a slightly rounded square wave. For 50Hz output frequency (mains frequency in Austria) change R1 and R2 to 68K and for 60Hz output frequency (mains frequency in United States) change R1 and R2 to 56K.
The maximum output current should not exceed about 100mA RMS (minimum load resistance 30 Ohms).
The value of the output capacitor, C4, is not critical: 220uF upwards would be OK. The working voltage of C4 should be 12V or higher.
The value of the decoupling capacitor, C3, is not critical either: 10uF upwards would be OK. The working voltage of C3 should be 15V or higher.
The frequency of the multivibrator is dictated by the values of R1 and R2, and C1 and C2. The best way to change the frequency of the multivibrator is to change C1 and C2. But you can also change the multivibrator frequency by changing R1 and R2, although the minimum value of R1 and R2 is about 10K and the maximum value of R1 and R2 is about 220K.
By the way, the general formula for the multivibrator frequency is 1/1.38RC Hz (R in Ohms and C in Farads) In the case of this multivibrator R is the value of R1 or R2 and C is the value of C1 or C2.
You can also change the mark to space ratio of the multivibrator by having different values for R1/C1 and R2/C2.
You can also try different supply line, but don't go over 12V.