Fret scanners and pickups for stringed instruments
Techniques are described that relate to various aspects of converting the mechanical energy of instrument strings to digital representations for use in a variety of applications.
1. A computer program product, comprising one or more non-transitory computer-readable media having computer program instructions stored therein, the computer program instructions being configured such that, when executed by one or more processors, the computer program instructions cause the one or more processors to:
receive fretting data representing fretting hand positions for strings of a stringed instrument;
receive string data representing vibrations of the strings of the stringed instrument;
determine a first fundamental frequency estimate for a first string of the stringed instrument by performing a spectral analysis of the string data for the first string;
determine a second fundamental frequency estimate for the first string using the fretting data for the first string;
determine that the first fundamental frequency estimate for the first string corresponds to a harmonic of the second fundamental frequency estimate for the first string; and
correct the first fundamental frequency estimate for the first string using the second fundamental frequency estimate for the first string.
2. The computer program product of claim 1 , wherein the computer program instructions are further configured to cause the one or more processors to:
determine a first fundamental frequency estimate for a second string of the stringed instrument by performing a spectral analysis of the string data for the second string;
determine a second fundamental frequency estimate for the second string using the fretting data for the second string;
initially report a pitch estimate for the second string based on the second fundamental frequency estimate for the second string;
after a delay, report the pitch estimate for the second string based on the first fundamental frequency estimate for the second string;
when an amplitude of the string data for the second string falls below a first threshold, lock a current value of the pitch estimate for the second string; and
when the amplitude of the string data for the second string falls below a second threshold, terminate reporting of the pitch estimate for the second string.
3. The computer program product of claim 1 , wherein the computer program instructions are further configured to cause the one or more processors to:
receive a bend signal for a second string of the stringed instrument, the bend signal indicating that the second string is bent parallel to a top surface of the stringed instrument; and
inhibit reporting of a pitch estimate for the second string based on the fretting data for the second string.
4. The computer program product of claim 3 , wherein the computer program instructions are further configured to cause the one or more processors to:
determine a fundamental frequency estimate for the second string by performing a spectral analysis of the string data for the second string; and
report a pitch estimate for the second string based on the fundamental frequency estimate for the second string.
5. The computer program product of claim 1 , wherein the computer program instructions are further configured to cause the one or more processors to:
receive a bend signal for a second string of the stringed instrument, the bend signal indicating that the second string is bent parallel to a top surface of the stringed instrument;
determine a fundamental frequency estimate for the second string using the fretting data for the second string; and
modify the fundamental frequency estimate for the second string using the bend signal.
6. The computer program product of claim 5 , wherein the computer program instructions are configured to cause the one or more processors to modify the fundamental frequency estimate for the second string by:
determining a displacement of the second string based on the bend signal; and
modifying the fundamental frequency estimate for the second string based on the displacement of the second string.
7. The computer program product of claim 1 , wherein the computer program instructions are further configured to cause the one or more processors to:
determine a first fundamental frequency estimate for a second string of the stringed instrument by performing a spectral analysis of the string data for the second string;
determine a second fundamental frequency estimate for the second string using the fretting data for the second string; and
where determination of the first fundamental frequency estimate for the second string takes longer than a programmable period of time, report a pitch estimate for the second string based on the second fundamental frequency estimate for the second string.
8. The computer program product of claim 1 , wherein the computer program instructions are further configured to cause the one or more processors to:
determine a first fundamental frequency estimate for a second string of the stringed instrument by performing a spectral analysis of the string data for the second string;
determine a second fundamental frequency estimate for the second string using the fretting data for the second string; and
where a signal level associated with the second string is below a threshold, report a pitch estimate for the second string based on the second fundamental frequency estimate for the second string.
9. The computer program product of claim 1 , wherein the computer program instructions are further configured to cause the one or more processors to:
determine a first fundamental frequency estimate for a second string of the stringed instrument by performing a spectral analysis of the string data for the second string;
determine a second fundamental frequency estimate for the second string using the fretting data for the second string;
generate a plurality of successive pitch estimates for the second string based on successive values of the first fundamental frequency estimate or the second fundamental frequency estimate; and
generate a smoothed pitch estimate for the second string using the plurality of pitch estimates.
10. The computer program product of claim 9 , wherein the computer program instructions are further configured to cause the one or more processors to determine a power of the second string, and to vary a number of the successive pitch estimates used to generate the smoothed pitch estimate based on the power of the second string.
11. The computer program product of claim 1 , wherein the computer program instructions are configured to cause the one or more processors to perform the spectral analysis of the string data for the first string by:
determining a discrete spectrum using a range of the string data for the first string;
determining a power spectral density for the range of the string data using the discrete spectrum;
extracting a plurality of harmonics from the power spectral density; and
identifying one of the harmonics as the first fundamental frequency estimate for the first string.
12. A device, comprising:
memory;
one or more interfaces configured to receive fretting data representing fretting hand positions for strings of a stringed instrument, the one or more interfaces also being configured to receive string signals representing vibrations of the strings of the stringed instrument;
circuitry for generating string data from the string signals; and
one or more processors configured in conjunction with the memory to:
determine a first fundamental frequency estimate for a first string of the stringed instrument by performing a spectral analysis of the string data for the first string;
determine a second fundamental frequency estimate for the first string using the fretting data for the first string;
determine that the first fundamental frequency estimate for the first string corresponds to a harmonic of the second fundamental frequency estimate for the first string; and
correct the first fundamental frequency estimate for the first string using the second fundamental frequency estimate for the first string.
13. The device of claim 12 , wherein the one or more processors are further configured to:
determine a first fundamental frequency estimate for a second string of the stringed instrument by performing a spectral analysis of the string data for the second string;
determine a second fundamental frequency estimate for the second string using the fretting data for the second string;
initially report a pitch estimate for the second string based on the second fundamental frequency estimate for the second string;
after a delay, report the pitch estimate for the second string based on the first fundamental frequency estimate for the second string;
when an amplitude of the string data for the second string falls below a first threshold, lock a current value of the pitch estimate for the second string; and
when the amplitude of the string data for the second string falls below a second threshold, terminate reporting of the pitch estimate for the second string.
14. The device of claim 12 , wherein the one or more processors are further configured to:
receive a bend signal for a second string of the stringed instrument, the bend signal indicating that the second string is bent parallel to a top surface of the stringed instrument; and
inhibit reporting of a pitch estimate for the second string based on the fretting data for the second string.
15. The device of claim 14 , wherein the one or more processors are further configured to:
determine a fundamental frequency estimate for the second string by performing a spectral analysis of the string data for the second string; and
report a pitch estimate for the second string based on the fundamental frequency estimate for the second string.
16. The device of claim 12 , wherein the one or more processors are further configured to:
receive a bend signal for a second string of the stringed instrument, the bend signal indicating that the second string is bent parallel to a top surface of the stringed instrument;
determine a fundamental frequency estimate for the second string using the fretting data for the second string; and
modify the fundamental frequency estimate for the second string using the bend signal.
17. The device of claim 16 , wherein the one or more processors are configured to modify the fundamental frequency estimate for the second string by:
determining a displacement of the second string based on the bend signal; and
modifying the fundamental frequency estimate for the second string based on the displacement of the second string.
18. The device of claim 12 , wherein the one or more processors are further configured to:
determine a first fundamental frequency estimate for a second string of the stringed instrument by performing a spectral analysis of the string data for the second string;
determine a second fundamental frequency estimate for the second string using the fretting data for the second string; and
where determination of the first fundamental frequency estimate for the second string takes longer than a programmable period of time, report a pitch estimate for the second string based on the second fundamental frequency estimate for the second string.
19. The device of claim 12 , wherein the one or more processors are further configured to:
determine a first fundamental frequency estimate for a second string of the stringed instrument by performing a spectral analysis of the string data for the second string;
determine a second fundamental frequency estimate for the second string using the fretting data for the second string; and
where a signal level associated with the second string is below a threshold, report a pitch estimate for the second string based on the second fundamental frequency estimate for the second string.
20. The device of claim 12 , wherein the one or more processors are further configured to:
determine a first fundamental frequency estimate for a second string of the stringed instrument by performing a spectral analysis of the string data for the second string;
determine a second fundamental frequency estimate for the second string using the fretting data for the second string;
generate a plurality of successive pitch estimates for the second string based on successive values of the first fundamental frequency estimate or the second fundamental frequency estimate; and
generate a smoothed pitch estimate for the second string using the plurality of pitch estimates.
21. The computer program product of claim 20 , wherein the one or more processors are further configured to determine a power of the second string, and to vary a number of the successive pitch estimates used to generate the smoothed pitch estimate based on the power of the second string.
22. The device of claim 12 , wherein the one or more processors are further configured to perform the spectral analysis of the string data for the first string by:
determining a discrete spectrum using a range of the string data for the first string;
determining a power spectral density for the range of the string data using the discrete spectrum;
extracting a plurality of harmonics from the power spectral density; and
identifying one of the harmonics as the first fundamental frequency estimate for the first string.