Differential filters: high pass, low pass, band pass
Am assuming that a differential-output instrumentation amplifier offers a low output impedance on both inverting and non-inverting outputs....something to check on its data sheet. Having low output impedance makes filter design easier.
In any case, consider adding a front-end low-pass filter to the instrumentation amp, if only to take out radio frequency components.
You may be able to concatenate low-pass and high-pass together as shown below. The two common-mode capacitors (C3cm, C4cm) represent stray capacitance, and are not real components. EMG signal frequency components of interest are likely below the megahertz region...the filter shown has high-pass and low-pass corner frequencies that may be inappropriate for your application (consider it as an example circuit arrangement only):


 Note that in this case, mid-band gain @ 796 Hz is near -3dB. With R1=R2=R3 and C1=C2=C3, you get about -14dB gain, and a narrow pass-band. If you need a band-pass bandwidth narrower than this, consider using LC filter components (not recommended).
Mid-band gain is highest when the low-pass corner frequency >> high-pass corner frequency. High mid-band gain and narrow pass-band are mutually exclusive with this RC arrangement. LC bandpass filters can be designed with narrow passband and high mid-band gain. The inductors of LC filters in the frequency range of EMG signals are rather large, and susceptible to ingress of interfering noise.